(;
GM[1]FF[4]VW[]AP[Many Faces of Go:11.0]
SZ[19]
HA[0]
ST[0]
PC["The Most Difficult Problem Ever"]
KM[0.0]
RU[Japanese]
SO[Created by Inoue Dosetsu Inseki (1646 - 1719)]
US[Compiled by Thomas Redecker]
EV[Igo Hatsuyoron]
CP[2011 Thomas Redecker]
RO[Problem 120]
AB[ra][pe][oe][le][lc][lb][ld][me][hb][fc][fe][de][ce][bf][bd]
[of][og][oh][oi][ph][qh][rh][sh][pi][ni][mi][lj][lk][rk][sk]
[ql][pl][qm][rm][sp][sq][qq][oo][pp][pq][pr][ps][os][ns][nr]
[ko][mn][aj][ak][al][am][bm][bs][cr][bp][cp][co][dn][ep][fq]
[fo][fn][em][el][ek][fj][dh][di][il][mf]
AW[qa][rb][qc][qe][re][od][nd][mb][jb][ib][hc][cd][jd][ke][kg]
[lg][ng][pf][nj][oj][pj][ok][qj][ri][si][rl][sl][sm][rn][ro]
[so][sn][rq][qp][qo][on][op][or][mr][ms][ah][bg][cg][dg][df]
[ff][gg][hg][hi][ki][jj][jn][jm][jl][jk][hm][hp][ir][kp][lp]
[mp][bn][cn][ap][ar][en][eq][bj][cj][dk][dl]
C[Let me give you a short introduction into what three amateurs
think might be the solution of Igo Hatsuyoron's problem #120.

I will not explain the standard moves of the "classical" solution
in detail here. If you are interested in, please refer to http://www.dgob.de/dgoz/trmdpe/index.htm#E,
for example.]
;B[po];W[rr];B[qk];W[ml];B[ll];W[mm];B[lm];W[nn]
;B[no];W[mo];B[ln];W[pn];B[qn];W[rp];B[ol];W[nl];B[nm];W[om]
(;B[mj]
C[We are unsure whether Black 19 might be played at 20 (= second
Throw-in). We were unable to find the Semeai, mentioned by Fujisawa
Shuko 9p, ending futile for Black thereafter.]
;W[nk];B[rj]
C[As far as I know, the exchange Black 21 - White 22 is shown in
the Chinese edition of Igo Hatsuyoron. It prevents a later exchange
of White 21 - Black 22 with Black's stone at 22 ending as White's
prisoner.]
;W[qi];B[np];W[rs];B[sr];W[oq];B[mq]
;W[lr];B[lq];W[kr];B[kq];W[jp];B[jq];W[jr];B[iq];W[hq];B[gr]
;W[hr];B[ip];W[jo];B[io];W[ho];B[in];W[hn];B[im];W[hl];B[ik]
;W[hk];B[ij];W[hj];B[ii];W[ih];B[ji];W[kj];B[jh];W[kh];B[jg]
;W[jf];B[ig];W[hh];B[if];W[ie];B[hf];W[he]
C[We think that Black must reduce White's top right corner before
playing the Crosscut sequence in the center.

Black can play the Guzumi of A now or start with the De of B,
which would result in a change in the order of moves.]
LB[pd:B][rg:A]

(;B[rg];W[rf];B[pd];W[pc];B[nb]
C[Black 69 is the Hasami-Tsuke of Harry Fearnley and can only be
played in conjunction with my Guzumi at 65.]
;W[mc];B[ma];W[ob]
C[The two false Eyes at A and B provide Black's top right group
with an additional external liberty, making it possible to connect
his pivotal stones of 69 and 71 later.]
LB[oc:A][qf:B]
;B[gf]
;W[ge];B[fg];W[ef];B[fh];W[hs];B[ee];W[cm];B[an];W[bo];B[ao]
;W[aq];B[bi];W[ai];B[bh];W[ag];B[bk];W[ck];B[bl];W[cl];B[ak]
;W[aj];B[bl];W[ao];B[am];W[bk];B[al];W[mg];B[dm];W[nc];B[na]
C[As mentioned before, Black is able to connect here, due to the
false Eyes of A and B.]
LB[oc:A][qf:B]

;W[oa];B[la];W[kb];B[eg];W[ka];B[dj];W[kc];B[af];W[ne];B[nf]
;W[lf];B[cf];W[qd];B[br];W[sf];B[bq];W[kn];B[as];W[lo];B[ch]
;W[li];B[ci];W[mh];B[bm];W[an];B[al];W[oc];B[ak];W[kd];B[bl]
;W[md];B[am];W[bm];B[al];W[fb]
C[White 138 is the Tsuke of Yamada Shinji 5p. It can be played
even at this early moment, because White could capture Black's
centre string in Sente at any time she likes.]
;B[eb]
C[Black cannot resist with 139 at 140, because White would be able
to reach a Seki in the top left corner thereafter.]
;W[gb];B[gc];W[ec];B[fa]
;W[ha];B[dc];W[gj]
C[As ususal, the Endgame on the left can be finished first.]
;B[fi];W[fr];B[er];W[fs];B[es];W[gs];B[gd]
;W[hd];B[ed];W[gq];B[fp]
C[A starts the Semeai version, which is the correct choice for
White here.

B captures Black's centre string and brings Joachim's Oki to
life.]
LB[nq:B][pk:A]

(;W[pk];B[mk];W[qg];B[nq];W[oq];B[ak];W[nh];B[bl];W[am]
;B[al];W[sg];B[ak];W[kk];B[qr];W[kl];B[qs];W[ss];B[sq];W[km]
;B[sp];W[pg];B[sr];W[tt]
C[Black has 77 points + 50 prisoners = 127 points.
White has 62 points + 63 prisoners = 125 points.

Black wins be 2 points.

Because White has captured Black's group in the top right, each
of Black's "reducing" moves there - if answered by a White one
- does not matter here. These reducing moves are necessary to
prevent White from choosing the Capture variation.]
)
(;W[nq];B[mq];W[oq]
C[White 160 is the Oki of Joachim Meinhardt, being the death blow
to the "classical" solution. This move gains 4 points for White.]
;B[qr];W[nq];B[qs];W[ss];B[sq];W[lq]
;B[sp];W[nh];B[sr];W[kk];B[pm];W[nm];B[pk];W[kl];B[sj];W[km]
;B[mk];W[tt]
C[Black has 62 points + 39 prisoners = 101 points.
White has 48 points + 48 prisoners = 96 points.

Black wins by 5 points here.

But be aware that the Guzumi destroyed 3 points of White's territory,
and the Hasami-Tsuke 4 points. Without these two moves (= the
"classical" solution), White would win by 2 points, due to Joachim's
Oki, which destroyed 4 points of Black's territory.]
TR[mq][op][oq][or]
SQ[qf][rf][sf][na][oa][ob][oc]
))
(;B[pd];W[pc];B[nb];W[mc];B[ma];W[ob];B[rg];W[rf];B[gf]
;W[ge];B[fg];W[ef];B[fh];W[hs];B[ee];W[cm]))
(;B[nk]))