(;AB[ao]AB[bo]AB[co]AB[cn]AB[cm]AB[cl]AB[ck]AB[bk]AB[ak]AW[aj]AW[bj]AW[cj]AW[dj]AW[dk]AW[dl]AW[dm]AW[dn]AW[do]AW[dp]AW[cp]AW[bp]AW[ap]C[FORCE]LB[ej:Y]LB[ek:N]AP[goproblems]
(;B[ek]C[]AW[ak]AW[bk]AW[ck]AW[cl]AW[cm]AW[cn]AW[co]AW[bo]AW[ao]AB[ap]AB[bp]AB[cp]AB[dp]AB[do]AB[dn]AB[dm]AB[dl]AB[aj]AB[cj]AB[bj]AB[dj]AB[dk];W[el]C[Kill it, then.]
(;B[am];W[bm]
(;B[al];W[an])
(;B[an];W[al]))
(;B[bm];W[am]
(;B[bl];W[bn])
(;B[bn];W[bl])
(;B[al];W[bl])
(;B[an];W[bn]))
(;B[an];W[am])
(;B[bn];W[bm])
(;B[al];W[am])
(;B[bl];W[bm]))
(;B[ej]C[];W[am]C[Now prove it.]
(;B[bm]
(;W[al]C[CHOICE]
(;B[an]C[RIGHT])
(;B[bl];W[an];B[bn];W[am]
(;B[al];W[an])
(;B[an];W[al])))
(;W[an]C[CHOICE]
(;B[al]C[RIGHT])
(;B[bn];W[al];B[bl];W[am]
(;B[al];W[an])
(;B[an];W[al]))))
(;B[al];W[bm])
(;B[an];W[bm])))