(;AB[dp]AW[qo]AW[qp]AW[pq]AW[nq]AB[po]AB[pn]AB[qn]AB[pj]AB[qh]AB[pd]AW[qc]AW[qd]AW[qf]AB[oc]AW[nc]AW[md]AB[mc]AB[nd]AB[ne]AW[cc]AW[cj]C[Capturing a stone at O18 is big, but so is reducing the corner at S15. What would you choose? (please play on a marked spot)FORCE]MA[nb]MA[re]AP[goproblems] (;B[re];W[qe]MA[rf]C[FORCE];B[rf];W[rd]C[FORCE]MA[qg];B[qg];W[pb]C[FORCE]MA[nb];B[nb];W[rb]C[Very good. Black fixed in sente and can now play a big move around F17.RIGHT]) (;B[nb];W[rf]C[Because black played a slow move, white can fix his group with this nice move.]))