Problem	13457
Created	2010-02-25
Source	Friend of mine on KGS gave it to me
Rating

Difficulty	8 dan
Average Solve Time	51 secs
User Attempts	28 / 175
Solve Ratio Rating	1 dan
	rating history

Feel free to give feedback about mistakes. I tried to make as many possible lines as I could. Note... this is a very hard problem

(;AB[bq]AB[cq]AB[cp]AB[cr]AB[dp]AB[ep]AB[fp]AB[gp]AB[hp]AB[ho]AB[fo]AB[fn]AB[gn]AB[hq]AW[dq]AW[eq]AW[fq]AW[gq]AW[aq]AW[br]AW[bp]AW[bo]AW[co]AW[eo]AW[en]AW[cm]AW[gm]AW[fm]AW[in]AW[jo]AW[jr]AW[jq]AW[hr]C[Black to get best result]AP[goproblems] (;B[gr];W[fr] (;B[dr] (;W[gs] (;B[er] (;W[cs] (;B[ds];W[ar];B[fs];W[es]C[Correct Solution. However w takes ko firstRIGHT]) (;B[fs];W[es];B[ds];W[ar];B[fs]C[Excellent. Best result -- Black takes ko firstRIGHT]) (;B[ar];W[as] (;B[fs];W[es];B[ds];W[ap];B[fs]C[Excellent. Black takes ko and has b1 ko threatRIGHT]) (;B[ds];W[ap];B[fs];W[es];B[bs];W[ar];B[fs]C[Excellent. Black takes ko firstRIGHT]))) (;W[es] (;B[ds] (;W[fs] (;B[ar];W[as];B[bs];W[cs]C[Correct. However there is slightly better ko. If instead of d1, you play a2 thrown in firstRIGHT]) (;B[bs];W[ar])) (;W[ar];B[fs]C[Excellent black takes ko firstRIGHT])) (;B[ar];W[as] (;B[bs];W[cs];B[ds] (;W[ap];B[bs];W[ar];B[fs]C[Excellent. Black takes ko firstRIGHT]) (;W[fs];B[bs]C[Excellent. 2 step ko for white, and black takes firstRIGHT])) (;B[ds];W[fs];B[bs];W[cs]C[Correct solution however w takes ko first. Navigate tree for better ko in this situationRIGHT])))) (;B[ar];W[as] (;B[er] (;W[es] (;B[bs];W[cs];B[ds];W[ap];B[fs]C[Excellent! Black takes ko first, and has b1 has local ko threatRIGHT]) (;B[ds];W[fs];B[bs];W[cs]C[Correct, however w takes ko firstRIGHT]) (;B[cs];W[ap])) (;W[cs] (;B[fs];W[es];B[ds];W[ap];B[fs]C[Excellent. Black takes ko and has b1 ko threatRIGHT]) (;B[ds];W[ap];B[fs];W[es];B[bs];W[ar];B[fs]C[Excellent. Black takes ko firstRIGHT])) (;W[fs] (;B[cs] (;W[ap];B[es]C[Excellent. Black lives this way.RIGHT]) (;W[es];B[bs]C[Excellent. Black lives this wayRIGHT])) (;B[es];W[cs]))) (;B[bs];W[cs] (;B[ds];W[ap];B[fs];W[es];B[er];W[gr]) (;B[er];W[gr];B[ds];W[ap])) (;B[fs];W[es];B[cs];W[ap]))) (;W[er];B[ds] (;W[ap];B[es];W[gs];B[fs];W[gr];B[ir]) (;W[gs];B[ar];W[as];B[bs];W[cs]C[Good ko for black, since black also has E1 ko threat]))) (;B[er];W[dr] (;B[ds];W[es] (;B[bs];W[ar]) (;B[ar];W[as];B[bs];W[cs])) (;B[cs];W[ap];B[ds] (;W[gs] (;B[ir];W[iq]) (;B[fs];W[es])) (;W[es];B[ir];W[gs]))) (;B[ar];W[as];B[dr];W[gs] (;B[er] (;W[es] (;B[bs];W[cs];B[ds];W[ap];B[fs]C[Excellent! Black takes ko first, and has b1 has local ko threatRIGHT]) (;B[ds];W[fs];B[bs];W[cs]C[Correct, however w takes ko firstRIGHT]) (;B[cs];W[ap])) (;W[cs] (;B[ds];W[ap];B[fs];W[es];B[bs];W[ar];B[fs]C[Excellent Black takes ko firstRIGHT]) (;B[fs];W[es];B[ds] (;W[ap];B[bs];W[ar]) (;W[fs];B[bs]C[Excellent. 2 step ko for white, and black takes firstRIGHT])))) (;B[cs];W[ap];B[er];W[es]))) (;B[er];W[gr] (;B[dr];W[ap] (;B[fr];W[fs];B[ir];W[iq]) (;B[cs];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs])) (;B[fr];W[dr];B[ds];W[ap]) (;B[cs];W[ap] (;B[dr];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs]) (;B[fr];W[dr]))) (;B[fr];W[gr];B[cs];W[ap] (;B[dr];W[er]) (;B[er];W[dr])) (;B[fs];W[gr] (;B[cs];W[ap]) (;B[ds];W[ap])) (;B[cs];W[ap] (;B[gr];W[fr];B[fs];W[gs]) (;B[fr];W[gr] (;B[dr];W[er]) (;B[er];W[dr])) (;B[er];W[gr] (;B[dr];W[es];B[fr];W[fs]) (;B[fr];W[dr]))) (;B[ds];W[ap];B[gr];W[fr];B[ir];W[gs];B[iq];W[is]) (;B[dr];W[gr];B[er];W[ap] (;B[fr];W[fs];B[ir];W[iq]) (;B[cs];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs])) (;B[es];W[gr]) (;B[ar];W[as] (;B[gr];W[fr];B[dr];W[gs] (;B[er] (;W[es]) (;W[cs] (;B[ds];W[ap];B[fs];W[es];B[bs];W[ar];B[fs]C[Excellent Black takes ko firstRIGHT]) (;B[fs];W[es];B[ds]))) (;B[cs];W[ap];B[er];W[es])) (;B[dr];W[gr] (;B[er];W[ap];B[cs];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs]) (;B[cs];W[ap];B[er];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs])) (;B[er];W[gr] (;B[dr];W[ap];B[cs];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs]) (;B[fr];W[dr];B[ds];W[ap];B[ir];W[iq]) (;B[cs];W[ap];B[dr];W[es];B[fr];W[fs];B[ds];W[ir];B[gs];W[fs])) (;B[fr];W[gr] (;B[dr];W[er]) (;B[er];W[dr];B[ds];W[ap];B[ir];W[iq])) (;B[cs];W[ap];B[gr];W[fr] (;B[ir];W[gs] (;B[is];W[iq]) (;B[iq];W[is];B[jp];W[kp])) (;B[dr];W[gs];B[er];W[es]) (;B[er];W[gs])) (;B[ds];W[ap] (;B[gr];W[fr];B[fs];W[gs]) (;B[ir];W[gr])) (;B[es];W[gr]) (;B[fs];W[gr])))