(;AW[pa]AW[pb]AW[pc]AW[qc]AW[rc]AW[rd]AW[ob]AB[oa]AB[na]AB[nb]AB[oc]AB[od]AB[pd]AB[qd]AB[re]AB[rf]AB[qe]C[Black to get the best result, seki is not an option]AP[goproblems] (;B[rb];W[sb] (;B[ra];W[sd]C[];B[sa]C[Thousand year ko. Black will have to fill the triangled square, take the ko and then play the square and white gets to take back first.]TR[se]MA[qa]) (;B[sd];W[ra])) (;B[ra];W[sd] (;B[rb];W[sb];B[sa]C[Thousand year ko. Black will have to fill the triangled square, take the ko and then play the square and white gets to take back first.]TR[se]MA[qa]) (;B[sb];W[rb]C[Seki])) (;B[sd];W[rb] (;B[sb];W[sc];B[ra];W[sa]C[White takes first, and even if you win the ko it's still bent four in the corner and white can play another ko]) (;B[ra] (;W[qa];B[sb];W[sa]TR[se]C[White gets to take first and has a local threat at the triangled pointRIGHT]) (;W[sc];B[qa];W[sa];B[sb];W[se];B[sa]TR[sf]TR[sd]C[White can start the ko at any time, but black can force with the triangled moves and takes back first.RIGHT]))) (;B[sb];W[rb] (;B[ra];W[sd]C[Seki]) (;B[sd];W[sc];B[ra];W[sa]C[White takes first, and even if you win the ko it's still bent four in the corner and white can play another ko])))