(;GM[1]FF[4]SZ[19]
GN[Black cannot escape]
PC[http://senseis.xmp.net/?BeginnerExercise98/Solution]AP[GoWiki:2009]
DT[2009-04-22]
C[Diagram from http://senseis.xmp.net/?BeginnerExercise98/Solution

Black cannot escape]
PL[B]

AB[on][ko][lo][mp][np][pp][kq][lq][mq][oq][qq][kr][or][pr]
AW[ln][mo][no][oo][po][lp][op][nq][lr][mr][nr][qr][os][ps]

;B[pq]C[B1]MN[1]
;W[rq]C[W2]MN[2]
;B[qp]C[B3]MN[3]
;W[qo]C[W4]MN[4]

;
)
