Problem	17543
Created	2013-12-14
Source
Rating

Difficulty	9 dan
Average Solve Time	21 secs
User Attempts	20 / 210
Solve Ratio Rating	3 dan
	rating history

All comments appreciated

(;AB[br]AB[cr]AB[cq]AB[bo]AB[cm]AB[cl]AB[cj]AB[eo]AB[fo]AB[hn]AB[in]AB[im]AB[jm]AB[km]AB[kn]AB[ln]AB[mn]AB[nn]AB[oo]AB[op]AB[oq]AB[np]AB[pq]AB[qp]AB[po]AB[rp]AB[qn]AB[sq]AB[rr]AB[mr]AB[mq]AB[lr]AB[kr]AB[lq]AB[jr]AB[js]AB[jq]AB[iq]AB[hr]AB[hs]AB[gs]AB[fr]AB[er]AW[bp]AW[bq]AW[co]AW[cn]AW[ar]AW[ep]AW[eq]AW[fq]AW[gq]AW[gr]AW[hq]AW[hp]AW[ip]AW[jp]AW[kp]AW[kq]AW[lp]AW[mp]AW[mo]AW[no]AW[on]AW[om]AW[ll]AW[jl]AW[il]AW[fm]AW[em]AW[dm]AW[ir]AW[ls]AW[ms]AW[nr]AW[nq]AW[or]AW[pr]AW[qr]AW[qq]AW[rq]C[Can Black kill white marked stones ?FORCE]LB[hj:YES]LB[jj:NO]AW[nm]AW[kl]AW[mm]AW[hm]AB[gn]AW[gm]AW[gp]AW[hl]TR[ep]TR[eq]TR[fq]TR[gq]TR[gr]TR[hq]TR[gp]TR[hp]TR[ip]TR[jp]TR[kp]TR[kq]TR[lp]TR[mp]TR[mo]TR[no]AB[ek]AP[goproblems] (;B[hj];W[jj]C[Prove it !] (;B[do];W[dr] (;B[ds];W[cp];B[dp];W[dq]C[White can live by seki or kill Black on bottom by favorable ko.] (;B[cs];W[bs];B[as];W[fs];B[es];W[bs];B[ns];W[fs];B[is];W[qs];B[os];W[sr];B[ss];W[ps];B[ns]) (;B[bs];W[aq]) (;B[aq];W[ap];B[cs];W[bs];B[as];W[fs];B[es];W[bs])) (;B[dq];W[ds];B[cs];W[dp]C[White is alive] (;B[es];W[cp];B[dn] (;W[ao]) (;W[bn];B[jo];W[ao];B[aq];W[bm])) (;B[bn];W[dn]))) (;B[cp];W[do];B[dp] (;W[jo]C[SekiCHOICE]) (;W[bn] (;B[ao];W[an];B[jo];W[dr];B[ds];W[dq];B[cs];W[bs];B[as];W[fs];B[es];W[bs]) (;B[jo];W[dr];B[ds];W[dq];B[cs]) (;B[dr];W[jo]))) (;B[dp];W[do] (;B[jo];W[dq];B[cp];W[dr];B[bn];W[dn];B[ap];W[fs] (;B[es];W[cs];B[aq];W[ns]C[Black dead everywhere]) (;B[is];W[ns])) (;B[dq];W[jo]C[Seki]) (;B[cp];W[jo]) (;B[bn];W[cp];B[dq];W[jo])) (;B[dn];W[dr] (;B[dq];W[ds];B[cs];W[dp];B[es];W[bn];B[ao];W[do];B[en];W[jo]) (;B[ds];W[cp];B[dq];W[dp];B[bn];W[jo]C[seki])) (;B[dq];W[dp]) (;B[bn];W[cp] (;B[dq];W[jo]) (;B[dp];W[dq];B[do];W[dr]) (;B[dn];W[dp];B[dr];W[jo])) (;B[dr];W[dp] (;B[cp];W[do]) (;B[dn];W[bn];B[ao];W[do];B[en];W[jo]) (;B[bn];W[do]))) (;B[jj]AW[il]AW[hl]AB[jj];W[hj]AW[cj]AB[hj]AW[jj]AW[cl]AB[hl]AB[il]AB[jl]AB[kl]AB[ll]AW[cm]AB[dm]AB[em]AB[fm]AB[gm]AB[hm]AW[im]AW[jm]AW[km]AB[mm]AB[nm]AB[om]AB[cn]AW[gn]AW[hn]AW[in]AW[kn]AW[ln]AW[mn]AW[nn]AB[on]AW[qn]AW[bo]AB[co]AW[eo]AW[fo]AB[mo]AB[no]AW[po]AW[oo]AB[bp]AB[ep]AB[gp]AB[hp]AB[ip]AB[jp]AB[lp]AB[kp]AB[mp]AW[np]AW[op]AW[qp]AW[rp]AB[bq]AW[cq]AB[eq]AB[fq]AB[gq]AB[hq]AW[iq]AW[jq]AB[kq]AW[lq]AW[mq]AB[nq]AW[oq]AW[pq]AB[qq]AB[rq]AW[sq]AB[ar]AW[br]AW[cr]AW[er]AW[fr]AB[gr]AW[hr]AB[ir]AW[jr]AW[kr]AW[lr]AW[mr]AB[nr]AB[or]AB[pr]AB[qr]AW[rr]AW[gs]AW[hs]AW[js]AB[ls]AB[ms]AW[do]TR[do]C[You're right, but prove it ! White played marked stone.] (;B[dr] (;W[ds]C[CHOICE] (;B[cp] (;W[dq]C[CHOICE];B[dp]C[];W[dn] (;B[bn]C[RIGHT];W[ao] (;B[jo]C[White deadRIGHT]) (;B[an];W[jo]C[SekiRIGHT]) (;B[ko]C[RIGHT]) (;B[io]C[RIGHT])) (;B[jo];W[bn]C[sente sekiRIGHT]) (;B[ao]C[RIGHT])) (;W[dp];B[dq];W[cs];B[bs];W[as];B[fs];W[es];B[bs])) (;B[dq];W[cp];B[dp];W[ap]LB[dn:A]LB[jo:B]C[dead. a and b miai] (;B[jo];W[dn]) (;B[dn];W[jo]))) (;W[dq] (;B[ds];W[cs];B[dp];W[es];B[cp];W[dn];B[bn];W[ao];B[jo]C[RIGHT]) (;B[dp];W[cp];B[ds]C[RIGHT]))) (;B[cp];W[dp];B[dq];W[dr] (;B[jo];W[dn]) (;B[dn];W[jo])) (;B[dp];W[cp] (;B[dr];W[ds];B[dq];W[ap]LB[dn:A]LB[jo:B]C[dead. a and b miai] (;B[jo];W[dn]) (;B[dn];W[jo])) (;B[dn];W[jo];B[dr];W[ds];B[dq];W[ap]) (;B[bn];W[ao] (;B[an];W[dq];B[jo];W[dn]C[False seki, you're dead];B[ap]) (;B[dn];W[jo];B[dr];W[ds];B[dq];W[ap])) (;B[jo];W[dn];B[bn];W[ao] (;B[dr];W[ds];B[dq]) (;B[an];W[dr]))) (;B[dn];W[dp];B[dq];W[cp];B[dr];W[ds]) (;B[dq];W[dr] (;B[cp];W[dp] (;B[jo];W[dn]) (;B[dn];W[jo])) (;B[jo];W[cp];B[dp];W[dn];B[bn];W[ao]C[Black dead. False seki]) (;B[dn];W[cp];B[dp];W[ap])) (;B[ns];W[dp];B[dq];W[cp];B[dr];W[ds])))