(;AB[sd]AB[qd]AB[rd]AB[qc]AB[qb]AB[pb]AB[oc]AB[od]AB[sb]AW[rb]AW[ra]AW[nb]AW[ob]AW[nc]AW[ne]AW[pc]AW[pd]AW[pe]AW[qe]AW[re]AW[se]C[Black to play.]AP[goproblems] (;B[pa] (;W[sa] (;B[rc]C[];W[sc]C[Ko for life, Black needs to find the first ko threat.RIGHT]) (;B[qa];W[sc]) (;B[sc]C[Black is dead. White can play at R19 any time and still leave a dead shape.])) (;W[rc];B[sc]C[Seki.RIGHT]) (;W[qa];B[rc]C[RIGHT]) (;W[sc];B[rc];W[oa]C[Seki.RIGHT])) (;B[rc];W[pa]LB[qa:A]C[Black suffers from a shortage of liberties and cannot play at A.]) (;B[qa];W[rc]C[This is not seki; if White removes the outside liberty Black is in atari.]MA[pa]MA[oa]))