(;
AB[le][me][ne][md][oh][nc][lc][lb][ma][na][ob][pb][rb][ra][sj][rj][qi][qh][qg][rg][ph][qb][nh][mg][lg][lf]
AW[qc][od][nb][oe][nf][mf][pg][qf][rf][si][og][nd][sb][rc]
C[Pro Pair Go Tsumego 3 (Answer)

Presented here is the answer to the 3rd tsumego from Michael Redmond 9P's coverage of the challenging tsumego problems featured at the 2016 pro pair go tournament.

The author of this tsumego is Kono Rin 9P.  Michael explains what you may notice as a curious part of this position:

"White's 2 non-attached stones do not change the problem's result, but have the effect of pruning one of two correct variations for Black at move 5 of the answer, and another alternative answer later in the correct sequence, thus limiting Black to only one variation throughout the entire correct answer.  In tsumego, there must be only one correct first move, but serious tsumego composers will avoid variations later in the answer as well."]
(;
B[sf]
C[Correct.];
W[se];B[qe]
TR[sf][se]
C[Black's tsuke is the vital point.  Playing the marked exchange first has the effect of reducing White's eye space.]
(;
W[sg]
C[White's correct move.  With this, White can get a ko.]
(;
B[qd]
C[Black's correct move.]
(;
W[pc]
C[White's correct move.]
(;
B[sc]
C[Black's correct move.]
(;
W[ng]
C[White's correct move];
B[pf];W[of];B[pd]
C[Threatens snap-back.];
W[oc]
(;
B[sa];W[sd]
(;
B[pe]
LB[sb:A]
C[Ko is the correct answer.  If White can win the ko at A, White will be alive with seki.  If Black wins the ko, White is dead with a five stone nakade.]
)
    (;
    B[rd]
    TR[nb]
    C[Mistake.  Without the marked stone this would be an alternative answer.];
    W[mc]
    C[White is alive.]
    )
)
    (;
    B[pe]
    C[Mistake.];
    W[sd]
    C[Alive with seki.]
    )
)
    (;
    W[sd]
    C[Mistake.];
    B[of];W[pf];B[ng]
    C[Dead.]
    )
)
    (;
    B[of]
    C[Mistake.];
    W[pf];B[ng];W[sc];B[rd];W[oc]
    C[This is alive with a seki.]
    )
)
    (;
    W[rd]
    C[Mistake.];
    B[sc];W[of];B[pc];W[pd];B[pe]
    C[Dead.]
    )
)
    (;
    B[re]
    C[Mistake.  Now White will live.];
    W[pf]
    (;
    B[sd];W[sf]
    LB[ng:A][sc:B]
    C[A and B are miai, so this is alive.]
    )
        (;
        B[ng];W[sc];B[pc];W[pd];B[rd];W[qd]
        C[Alive with seki.]
        )
    )
    (;
    B[pc]
    TR[si]
    C[Mistake.  In this variation the marked White stone comes into play.];
    W[qd]
    (;
    B[re];W[sc]
    (;
    B[pf];W[sf]
    LB[sh:A][sd:B][si:C]
    C[If only Black could play an atari at A and force White to connect at B, there would be a way to kill this, so the stone at C works in this variation.];
    B[of];W[pe];B[of];W[rd]
    C[Alive.]
    )
        (;
        B[rd];W[of]
        C[Alive.]
        )
    )
        (;
        B[sc];W[sd];B[re];W[of];B[pe];W[pd]
        C[Alive with seki.]
        )
    )
)
    (;
    W[re]
    C[Mistake.  This will die.];
    B[qd]
    TR[of]
    C[Black is always looking at the marked throw-in, but it must be saved until the timing is correct.];
    W[pd];B[sc]
    (;
    W[ng];B[pf];W[of];B[rd]
    C[Double atari kills.]
    )
        (;
        W[of];B[pc];W[sd];B[pe]
        C[Dead.]
        )
        (;
        W[sd];B[of];W[pf];B[ng]
        C[Dead.]
        )
    )
    (;
    W[pf]
    TR[ng][sc]
    C[White tries to make miai of the 2 marked points, but this will fail.];
    B[qd]
    (;
    W[rd];B[sc];W[ng];B[re];W[sg];B[pc]
    C[Dead.]
    )
        (;
        W[sc];B[pc];W[pd];B[rd]
        (;
        W[sd];B[ng]
        C[Dead.]
        )
            (;
            W[ng];B[sd]
            C[Dead.]
            )
        )
        (;
        W[pc];B[ng];W[sc];B[rd]
        C[This might look almost like a seki, but since White's stones are not completely connected, White will end up playing inside and dying.]
        (;
        W[re];B[pd]
        C[Dead.]
        )
            (;
            W[pd];B[re]
            C[Dead.]
            )
            (;
            W[sg];B[oc]
            LB[pd:A][re:B]
            C[A and B are miai.]
            )
        )
    )
)
    (;
    B[qe]
    C[This looks like a tesuji, but comes too soon, and is incorrect.];
    W[re];B[sf];W[qd];B[sd];W[pe];B[of];W[pf];B[ng];W[pc]
    C[Alive.]
    )
    (;
    B[re]
    C[This also may look like good shape, but fails.];
    W[se];B[qe];W[pf];B[ng];W[sc];B[pc];W[pd];B[rd];W[qd]
    C[Alive with seki.]
    )
)

