How many external ko threats does White need for life? Play at K (that will appear) when you want to use a ko threat. But you must use as less number of them as possible!
(;AB[ps]AB[os]AB[or]AB[oq]AB[op]AB[on]AB[po]AB[qn]AB[rn]AW[ro]AW[pp]AW[pq]AW[pr]AW[qs]AW[rr]AB[rs]C[Please read the instruction above. White to live using as few external ko threats as possible.]AB[rm]AP[goproblems]
(;W[qq];B[qr]LB[ms:K]C[Play at K if you need a ko threat now.]
(;W[ms];B[ns];W[qs];B[rp]
(;W[rq];B[qr]LB[mr:K]C[Play at K if you need a ko threat now.]
(;W[sr];B[sp]
(;W[qs]C[Nice!RIGHT])
(;W[so];B[qs]))
(;W[sp];B[sr]
(;W[qs]C[];B[qo]
(;W[ss]C[Nice!RIGHT])
(;W[qp];B[qr]LB[mr:K]C[Play at K for a ko threat.];W[mr];B[nr];W[qs]C[You lived, but you used too many ko threats.]))
(;W[qp];B[qs])
(;W[qo];B[qs])
(;W[sq];B[qs]))
(;W[mr];B[nr];W[qs]C[You lived, but you used too many ko threats.])
(;W[qp];B[qs];W[sp];B[sr])
(;W[qo];B[qs];W[sp];B[sr])
(;W[so];B[qs]
(;W[sr];B[sp])
(;W[sp];B[sr])))
(;W[ss];B[rq])
(;W[qp];B[qr]LB[mr:K]C[Play at K if you need a ko threat now.]
(;W[mr];B[nr];W[qs];B[rq]C[You can live with yet another ko threat, that is too many.])
(;W[sp];B[qs])
(;W[rq];B[qs];W[sp];B[sr]))
(;W[qo];B[rq]
(;W[sp];B[sq]
(;W[sr];B[so])
(;W[so];B[sn]))
(;W[sq];B[so]))
(;W[sp];B[rq]
(;W[qp];B[qr]C[Play at K for a ko threat.]LB[mr:K]
(;W[mr];B[nr];W[qs];B[qo];W[sq];B[qr]C[You can live with yet another ko threat, that is too many.])
(;W[sq];B[qs]))
(;W[sq];B[qr]C[Play at K for a ko threat.]LB[mr:K]
(;W[mr];B[nr];W[qs];B[qo];W[qp];B[qr]C[You can live with yet another ko threat, that is too many.])
(;W[qp];B[qs]))
(;W[ss];B[qp]))
(;W[sq];B[qr]C[Play at K for a ko threat.]LB[mr:K];W[mr];B[nr];W[qs];B[rq]
(;W[sp];B[qr]C[You can live with yet another ko threat, that is too many.])
(;W[qp];B[qr]C[You can live with yet another ko threat, that is too many.])
(;W[ss];B[qp]))
(;W[qr]C[You died in gote.]))
(;W[rp];B[qs];W[qo];B[sr];W[sq];B[rq]C[Play at K if you need a ko threat now.]LB[ms:K]
(;W[ms];B[ns];W[rr];B[ss];W[so];B[rq]C[Play at K if you want to use a ko threat.]LB[mr:K];W[mr];B[nr];W[rr]C[You lived, but you used too many ko threats.])
(;W[so];B[qp]))
(;W[qo];B[rp];W[qs];B[rq]
(;W[sp];B[sq]
(;W[sr];B[so])
(;W[so];B[sn]))
(;W[sq];B[so])
(;W[so];B[qp]))
(;W[sq];B[qs]
(;W[rp];B[qo]
(;W[qp];B[so])
(;W[so];B[qp]))
(;W[qo];B[rp]))
(;W[rq];B[qs]
(;W[sp];B[sr])
(;W[sr];B[sp]))
(;W[sp];B[qs]
(;W[sr];B[qp]
(;W[rq];B[qo])
(;W[qo];B[rq]))
(;W[rq];B[sr])
(;W[qo];B[rq]))
(;W[sr];B[qs]
(;W[rp];B[qo])
(;W[qo];B[rq])
(;W[sp];B[qp];W[rq];B[qo])
(;W[rq];B[sp])))
(;W[rp];B[qr];W[qq];B[qs];W[qo];B[sr];W[sq];B[rq]C[Play at K if you need a ko threat now.]LB[ms:K]
(;W[ms];B[ns];W[rr];B[ss];W[so];B[rq]C[Play at K if you want to use a ko threat.]LB[mr:K];W[mr];B[nr];W[rr]C[You lived, but you used too many ko threats.])
(;W[so];B[qp]))
(;W[ss];B[rq]C[You are dead. See Problem #597.])
(;W[rq];B[qr])
(;W[qo];B[qr])
(;W[qp];B[qr])
(;W[qr];B[rp]
(;W[qp];B[rq])
(;W[rq];B[qp]))
(;W[sq];B[qr];W[qq];B[qs]
(;W[rp];B[qo]
(;W[qp];B[so])
(;W[so];B[qp]))
(;W[qo];B[rp])))