1.F6 is the move.

Black has two groups that he must save in order to win: the six-stone group in the lower right and the eight-stone group running down the middle left. The former group can be saved by playing 1.B2, since that would ensure a connection to two sides in a home corner; however when White replies 2.E5, the latter group cannot live and the best Black can do is lose by about ten points.

After 1.F6 is played, the two endangered groups are sure to be connected into a single large group that White cannot kill. If White plays 2.K13, Black can play 3.B2 and live. Or if White plays 2.B2 himself, then Black can play 3.L13 --- now Black lives by either connecting to the stones at N15 and M15 (and thus having a group guaranteed to touch two opposite sides) or by escaping to M12. White can do no better than lose by five to ten points.