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Offline unkx80
 Post subject: 2010 April 20 problem
Post #1 Posted: Tue Apr 20, 2010 12:28 am 
Lives with ko

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My first post on this forum. What is the difficulty of this problem?



White to play.

EDIT: Looks like it is now possible to use SL diagram codes instead.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X . . . . X O O X . . |
$$ | . . . O . . . X . . . . . . . . . . . |
$$ ---------------------------------------[/go]

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Last edited by unkx80 on Wed Apr 21, 2010 1:35 am, edited 4 times in total.
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Offline Loons
 Post subject: Re: 2010 April 20 problem
Post #2 Posted: Tue Apr 20, 2010 5:00 am 
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I see a two step ko fairly directly, and I'm 5 kyu, but I tend to be terrible at problems.

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Offline Chew Terr
 Post subject: Re: 2010 April 20 problem
Post #3 Posted: Tue Apr 20, 2010 7:25 am 
Gosei
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I have an attempt:

Black seems to have no real answer to L1.

If L2, M2 then K2 after black connects.
If K2, K1 then sacrifice the two stones and make the eye false.

Not at all sure if my answer is right, but I'm 7k, as an estimate for what rank it is.

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Offline runaway
 Post subject: Re: 2010 April 20 problem
Post #4 Posted: Tue Apr 20, 2010 7:32 pm 
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Okay so I was thinking White L2 first, then K2, K1, M2, M1 ko but 1,2,3 popped into my head as is said on sensei's so I went to see K1 first. It kills without any complications. The problem should be around 5 kyu KGS with reading and 2 kyu KGS on blitz.

EDIT: corrected popped from the word with double o's :oops:

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Offline Solomon
 Post subject: Re: 2010 April 20 problem
Post #5 Posted: Tue Apr 20, 2010 9:48 pm 
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Chew Terr wrote:
I have an attempt:

Black seems to have no real answer to L1.

If L2, M2 then K2 after black connects.
If K2, K1 then sacrifice the two stones and make the eye false.

Not at all sure if my answer is right, but I'm 7k, as an estimate for what rank it is.

Black can just K1 and live.
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Offline unkx80
 Post subject: Re: 2010 April 20 problem
Post #6 Posted: Wed Apr 21, 2010 1:21 am 
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So far, none of the attempts are correct. I think this problem might be of dan level.
Now that diagrams are enabled, please post diagrams instead. I find it difficult to read coordinates. Thanks!

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Offline SoDesuNe
 Post subject: Re: 2010 April 20 problem
Post #7 Posted: Wed Apr 21, 2010 2:41 am 
Gosei
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runaway
I think K1 doesn't work because of...

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 2 . 4 5 X O O X . . |
$$ | . . . O 7 8 . X . 1 3 6 . . . . . . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wc White to play
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O b . X . |
$$ | . . O X X X X X X 2 8 4 6 X O O X . . |
$$ | . . . O . . . X 0 1 3 5 9 7 a . . . . |
$$ ---------------------------------------[/go]


White a, Black b, White loses all the stones.



My try:
Click Here To Show Diagram Code
[go]$$Wc White to play
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 2 1 4 . X O O X . . |
$$ | . . . O . . . X . 3 . 5 . . . . . . . |
$$ ---------------------------------------[/go]


The obvious Ko. ^^

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Offline unkx80
 Post subject: Re: 2010 April 20 problem
Post #8 Posted: Wed Apr 21, 2010 2:48 am 
Lives with ko

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To all: ko is not the solution.

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Offline Marcus
 Post subject: Re: 2010 April 20 problem
Post #9 Posted: Wed Apr 21, 2010 6:00 am 
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Guess I'll have to give this a go ... I had no trouble solving it, and I'm 4k KGS ... granted, I read well sometimes. Maybe 3-5k level problem?

EDIT: zinger pointed out a problem with my solution. I fixed it, so I'm adding it to this as well. Maybe the problem is a little harder than I thought ...

First move is obvious, I think:
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X . . . . X O O X . . |
$$ | . . . O . . . X . 1 . . . . . . . . . |
$$ ---------------------------------------[/go]


This is an immediate threat to the life of the Black group. White must respond. Variations below:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 2 . 3 . X O O X . . |
$$ | . . . O . . . X . 1 . . . . . . . . . |
$$ ---------------------------------------[/go]


(above) Easiest way to kill. White can easily falsify Black's eye, and is not in danger of losing his stones.

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 3 4 2 5 X O O X . . |
$$ | . . . O 7 9 . X 6 1 8 . . . . . . . . |
$$ ---------------------------------------[/go]


(above) White 1 and 3 are captured, but Black has only a single eye and is dead. Note that Black cannot play 8 at 9, because then ther is no way to approach White 1 or White 3 (Golden Chicken! My favourite shape!)

(below) White's last meaningful response that I can see ...

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X . 2 . . X O O X . . |
$$ | . . . O 3 . . X . 1 . . . . . . . . . |
$$ ---------------------------------------[/go]


White might play from here in one of two ways ...

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O 3 4 . X b 1 5 7 a . . . . . . |
$$ ---------------------------------------[/go]


(above) We get another Golden Chicken shape, wher Black cannot play at a or b.

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O B O . . X . |
$$ | . . O X X X X X X . 2 . . B O O X . . |
$$ | . . . O 3 5 . X . 1 4 . . . . . . . . |
$$ ---------------------------------------[/go]


(above) No matter what, White will capture the two marked Black stones. Black is reduced to a single eye.


EDIT:
As pointed out by zinger, in one of my diagrams, Black lives with some of his stones ... so I found a better way to play it. First, the diagram involved:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . a O 3 4 . X . 1 5 7 . b . . . . . |
$$ ---------------------------------------[/go]


Black can take the two White stones by playing at a. If White falsifies that eye, Black is no longer bound by my Golden Chicken shape and can approach the stones at White 1, capturing them. White's best move is to capture the chain of Black stones with b and Black gest a smaller group with a 2nd eye.

There is a better way, though. White has a better move 3:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X . 2 . . X O O X . . |
$$ | . . . O . 3 . X . 1 . . . . . . . . . |
$$ ---------------------------------------[/go]

Looks a bit funny, right? However, it threatens to really take that eye away:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X . 2 . . X O O X . . |
$$ | . . . O 5 3 . X . 1 4 . . . . . . . . |
$$ ---------------------------------------[/go]

No more eye.

So, Black needs to respond. Two responses preserve the eye:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O 4 3 . X . 1 5 7 . . . . . . . |
$$ ---------------------------------------[/go]

Golden Chicken makes a comeback!

The other way to preserve an eye:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O a 3 4 X . 1 5 7 . . . . . . . |
$$ ---------------------------------------[/go]

And again we have our Golden Chicken. It's important to note that White did not connect at a. There's a proverb: "Capture 3 on the edge to make an eye". Black can get his eye no matter what, so White needs to continue to play forcing moves. Playing at a does not force Black. Here's the failure line:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X . 2 . . X O O X . . |
$$ | . . 6 O 5 3 4 X . 1 . . . . . . . . . |
$$ ---------------------------------------[/go]

And then:

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 7 B 4 6 X O O X . . |
$$ | . . W 1 2 . B X 8 W 3 5 . . . . . . . |
$$ ---------------------------------------[/go]


Because White 1 in the second diagram is captured, Black gets both his eye and the ability to approach at Black 8.


Last edited by Marcus on Wed Apr 21, 2010 7:12 am, edited 1 time in total.
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Offline zinger
 Post subject: Re: 2010 April 20 problem
Post #10 Posted: Wed Apr 21, 2010 6:23 am 
Lives in gote
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Rank: hopeless
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O 3 4 . X b 1 5 7 a . . . . . . |
$$ ---------------------------------------[/go]

Interesting but black can capture two stones to the left with 10, living. Although even this feels like a success for white. But if white can truly kill, this feels like it is on the right track.

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Offline Marcus
 Post subject: Re: 2010 April 20 problem
Post #11 Posted: Wed Apr 21, 2010 6:56 am 
Gosei

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Was liked: 111
GD Posts: 209
KGS: Marcus316
zinger wrote:
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O 3 4 . X b 1 5 7 a . . . . . . |
$$ ---------------------------------------[/go]

Interesting but black can capture two stones to the left with 10, living. Although even this feels like a success for white. But if white can truly kill, this feels like it is on the right track.

Perhaps 9 to the right of a?


I tried the suggested 9, but it loses to the time-honored "one-eye-vs-no-eye" rule.
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O b . X . |
$$ | . . O X X X X X X 0 2 6 8 X O O X . . |
$$ | . . . O 3 4 . X d 1 5 7 a 9 c . . . . |
$$ ---------------------------------------[/go]


Guess this is not the answer, though White gains a good deal. White 3 looks like the problem. Here's another try, then ...

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O 4 3 . X . 1 5 7 . . . . . . . |
$$ ---------------------------------------[/go]


Looks better. Try a different Black 4 now ...

Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . O . . . . . . . . . O X . |
$$ | . . . . . . . O O O . O . O O O X . . |
$$ | . . . O O O O X O X O . . O X X X . . |
$$ | . O . O X X O X O X X O O X O . . X . |
$$ | . . O X X X X X X 9 2 6 8 X O O X . . |
$$ | . . . O . 3 4 X . 1 5 7 . . . . . . . |
$$ ---------------------------------------[/go]



Golden Chicken again. :D Looks like I got it.
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Offline unkx80
 Post subject: Re: 2010 April 20 problem
Post #12 Posted: Wed Apr 21, 2010 12:30 pm 
Lives with ko

Posts: 257
Location: Singapore
Liked others: 13
Was liked: 30
Rank: Dan player
Marcus' modified attempt is the solution. :)
So, given the attempts on SL and here, I think I should lower the difficulty rating a bit: probably 3 kyu to 1 dan.

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