(;AB[sl]AB[rl]AB[qk]AB[qj]AB[qi]AB[rh]AW[rm]AW[qn]AW[ql]AW[pl]AW[pk]AW[pi]AW[oi]AW[qh]AW[qg]AW[qf]AW[qd]C[White to unconditionally kill Black. A ko will be counted as failure.Hint: What is the vital point of Black's shape?]AP[goproblems]
(;W[sj];B[si]
(;W[rj]C[CHOICE];B[rg];W[sg];B[rf];W[re];B[sf];W[ri];B[rk];W[sh];B[si];W[sh]C[Now, White has killed Black unconditionally! Can you read out the shape?RIGHT])
(;W[sh];B[sg]
(;W[rg];B[rj];W[sf];B[sk];W[sh];B[ri])
(;W[rj];B[rg];W[sk];B[rk];W[sm];B[ri])))
(;W[rg];B[sh]
(;W[sj];B[rj]
(;W[sg];B[sk])
(;W[sm];B[si])
(;W[si];B[sk])
(;W[sk];B[si]))
(;W[rj];B[sj]
(;W[ri];B[rk])
(;W[rk];B[ri]))
(;W[sg];B[rj];W[sj];B[sk]))
(;W[sh];B[rg];W[sj];B[si];W[ri];B[rj]C[Black can manage a ko for life.])
(;W[sm];B[rj]C[Black unconditionally lives.])
(;W[rj]
(;B[sj]C[CHOICE]
(;W[rg];B[ri];W[sh];B[rk];W[sg];B[si])
(;W[ri];B[si]
(;W[pj];B[rk];W[ri];B[rj];W[rg];B[sh])
(;W[rg];B[rk]))
(;W[rk];B[sk]
(;W[pj];B[ri]
(;W[rg];B[sh])
(;W[sh];B[rg];W[rf];B[sg]))
(;W[ri];B[si];W[rj];B[rg];W[rf];B[sg]))
(;W[sk];B[rk];W[ri];B[si])
(;W[si]
(;B[sk];W[ri];B[rg])
(;B[ri];W[pj];B[rk];W[rg];B[sh])))
(;B[ri]
(;W[rg];B[sj];W[sh];B[rk];W[sg];B[si])
(;W[sj];B[rg]
(;W[rk];B[si];W[sm];B[sk])
(;W[rf];B[sg]
(;W[rk];B[si];W[sm];B[sk])
(;W[si];B[rk]C[];W[sk];B[sh];W[sj]C[])))))
(;W[ri];B[si]
(;W[rj];B[sj];W[pj];B[rk];W[rg];B[sh])
(;W[sj];B[rj])
(;W[rk];B[rj])))