build_0_2 2 6
build_0_21 0 7
build_0_6 3 15
build_12_5 0 7
build_21_12 0 7
build_2_3 2 6
build_3_4 2 6
build_4_5 2 6
build_6_7 3 4
build_7_5 3 4
