(;AB[nd][ne][nf][od][pd][qc][rc][sc][qe][ha][hb][hc][ic][ib][jc][kc][lc][mc][mb][lb][la]AW[sb][rb][qb][pc][oc][nc][nb][ld][kd][jd][id][hd][gc][gb][me][mf][ka][kb][jb][ia][md]C[Black to play and kill White's corner.](;B[oa];W[na](;B[pb];W[qa](;B[sa]C[Correct! White can't approach! RIGHT])(;B[ra]C[Correct! White can't approach! RIGHT])(;B[pa];W[ob]C[...ok?])(;B[ob];W[pa]C[...ok?])(;B[ma];W[ga]C[Whoops :(])(;B[ja];W[pa]C[Black was already alive. Black could've killed, but not anymore.]))(;B[qa];W[pb](;B[pa];W[ra])(;B[ra];W[pa]))(;B[pa];W[qa])(;B[ob];W[pa])(;B[ra];W[pa])(;B[sa];W[pa])(;B[ma];W[ga])(;B[ja];W[pa]))(;B[na];W[oa](;B[pb];W[ma]C[If Black wants any hope of killing White now, they will have to fight this disadvantageous ko for both groups.])(;B[ma];W[ga])(;B[pa];W[pb];B[ob];W[qa])(;B[ob];W[pb])(;B[qa];W[pb])(;B[ra];W[pb])(;B[sa];W[pb]))(;B[sa];W[pa]C[Not going to work.])(;B[ra];W[pa])(;B[qa];W[pa])(;B[pa];W[oa](;B[qa];W[pb])(;B[pb];W[qa])(;B[ra];W[pb])(;B[na];W[pb];B[ob];W[qa])(;B[ob];W[pb])(;B[ma];W[pb])(;B[sa];W[pb]))(;B[ja];W[pa]C[Your group was already alive. White could not take the vital point for it would be suicide. But White lives now.])(;B[ob];W[oa])(;B[pb];W[pa])(;B[ma];W[pa]))