Try to save all the marked stones, ko is not enough.
Enjoy
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[White]PB[Black]AW[fb][gb][hb][kb][lb][ob][ec][hc][jc][lc][oc][fd][gd][id][jd][ld][nd][ee][ne][oe][df][hf][eg][gg][hg][jg][kg][lg][mg][fh][nh][oh][qh][rh][hi][qi][ij][nj][pj][kk][mk][pk]AB[ia][ja][ka][la][jb][mb][pb][ic][mc][nc][pc][hd][md][od][pd][qd][ge][he][ie][pe][ef][gf][if][pf][ig][ng][og][pg][qg][ih][jh][kh][lh][mh]TR[ia][ja][ka][la][jb][mb][mc][nc][hd][md][ge][he][ie][gf][if][ig][ih][jh][kh][lh][mh]
(;B[ke]CR[ke]
;W[le]CR[le]
(;B[mf]CR[mf]C[Almost... but not quite]
;W[lf]CR[lf]
(;B[kd]CR[kd]C[WRONG]
;W[ib]CR[ib]
(;B[kc]CR[kc]
;W[je]CR[je])
(;B[kf]CR[kf]
;W[kc]CR[kc]))
(;B[ib]CR[ib]
;W[ha]CR[ha]
;B[ma]CR[ma]
;W[me]CR[me]
;B[oa]CR[oa]
;W[kd]CR[kd]LB[ke:A][mf:B]C[WRONG w can make 2 eyes, at A or B]))
(;B[kf]CR[kf]C[WRONG]
;W[me]CR[me]
;B[ib]CR[ib]
;W[ha]CR[ha]
;B[ma]CR[ma]
;W[na]CR[na]))
(;B[mf]CR[mf]
;W[ke]CR[ke]
;B[kf]CR[kf]
;W[lf]CR[lf]
(;B[me]CR[me]
;W[le]CR[le]
;B[ib]CR[ib]
;W[jf]CR[jf]C[WRONG])
(;B[jf]CR[jf]
;W[le]CR[le]
;B[ib]CR[ib]
;W[me]CR[me]
;B[nf]CR[nf]
;W[ha]CR[ha]
;B[ma]CR[ma]
;W[na]CR[na]C[WRONG]))
(;B[le]CR[le]
;W[ke]CR[ke]C[M15 to the resque!]
(;B[kf]CR[kf]C[WRONG]
;W[me]CR[me]
(;B[lf]CR[lf]
;W[jf]CR[jf])
(;B[mf]CR[mf]
;W[lf]CR[lf]
;B[nf]CR[nf]
;W[jf]CR[jf]))
(;B[kd]CR[kd]
;W[kc]CR[kc]C[CHOICE]
;B[je]CR[je]
;W[ib]CR[ib]C[W cuts his losses]
;B[kf]CR[kf]
;W[me]CR[me]
;B[kd]CR[kd]
;W[ap]CR[ap]LB[bp:A]C[play at A to aswer W ko threat]
;B[bp]CR[bp]
;W[ke]CR[ke]LB[lf:A]C[Play at A, black has no big enough ko threat]
;B[lf]CR[lf]
;W[mf]CR[mf]
;B[kd]CR[kd]
;W[aq]CR[aq]LB[bq:A]C[Play at A to answer w ko threat]
;B[bq]CR[bq]
;W[ke]CR[ke]
;B[jf]CR[jf]
;W[nb]CR[nb]C[WRONG w needs 2 huge ko threats, but there is a way to avoid ko.])
(;B[je]CR[je]C[CHOICE ]
(;W[kf]CR[kf]C[CHOICE]
;B[kd]CR[kd]
;W[ib]CR[ib]
;B[kc]CR[kc]C[RIGHT its an ex-w group])
(;W[kd]CR[kd]C[CHOICE]
;B[kf]CR[kf]
;W[ib]CR[ib]
;B[me]CR[me]C[RIGHT yes, cheer!])
(;W[me]CR[me]C[CHOICE]
;B[kd]CR[kd]
(;W[lf]CR[lf]
;B[kc]CR[kc]C[RIGHT this w group is no more])
(;W[ib]CR[ib]
;B[kc]CR[kc]C[RIGHT this w group is no longer under the living]))
(;W[ib]CR[ib]C[CHOICE]
;B[kf]CR[kf]C[CHOICE]
(;W[me]CR[me]C[CHOICE]
;B[kd]CR[kd]
;W[ic]CR[ic]
;B[kc]CR[kc]C[RIGHT w is finished])
(;W[kd]CR[kd]
;B[me]CR[me]C[RIGHT hoeray!])
(;W[ha]CR[ha]
;B[ma]CR[ma]
;W[kd]CR[kd]
;B[me]CR[me]C[RIGHT quite right!]))
(;W[lf]CR[lf]C[CHOICE w m14 is a mistake]
;B[kd]CR[kd]
;W[me]CR[me]
;B[kc]CR[kc]C[RIGHT this w group has ceased to exist])))
(;B[kf]CR[kf]C[when youve got enough spare time try this one...])
(;B[ib]CR[ib]C[WRONG]
;W[ha]CR[ha]
(;B[ma]CR[ma]
;W[me]CR[me]
;B[oa]CR[oa]
;W[ke]CR[ke]
(;B[kf]CR[kf]
;W[jf]CR[jf]
;B[lf]CR[lf]
;W[mf]CR[mf]C[WRONG w lives])
(;B[je]CR[je]
;W[lf]CR[lf]
;B[nf]CR[nf]
;W[mf]CR[mf]
;B[jf]CR[jf]
;W[kf]CR[kf]C[WRONG w lives])
(;B[mf]CR[mf]
;W[lf]CR[lf]
;B[nf]CR[nf]
;W[jf]CR[jf]C[WRONG w lives])
(;B[lf]CR[lf]
;W[mf]CR[mf]C[WRONG w lives]))
(;B[le]CR[le]
;W[ke]CR[ke]
;B[je]CR[je]
;W[ma]CR[ma]
;B[kf]CR[kf]
;W[me]CR[me]
;B[mf]CR[mf]
;W[lf]CR[lf]C[WRONG])))