YES Problem: a(a(b(b(x1)))) -> b(b(b(a(a(a(a(a(x1)))))))) Proof: String Reversal Processor: b(b(a(a(x1)))) -> a(a(a(a(a(b(b(b(x1)))))))) Bounds Processor: bound: 3 enrichment: match automaton: final states: {1} transitions: a1(50) -> 51* a1(40) -> 41* a1(15) -> 16* a1(52) -> 53* a1(42) -> 43* a1(17) -> 18* a1(49) -> 50* a1(44) -> 45* a1(14) -> 15* a1(51) -> 52* a1(41) -> 42* a1(16) -> 17* a1(53) -> 54* a1(43) -> 44* a1(13) -> 14* b1(10) -> 11* b1(47) -> 48* b1(37) -> 38* b1(12) -> 13* b1(39) -> 40* b1(46) -> 47* b1(11) -> 12* b1(48) -> 49* b1(38) -> 39* a2(152) -> 153* a2(112) -> 113* a2(87) -> 88* a2(77) -> 78* a2(149) -> 150* a2(114) -> 115* a2(89) -> 90* a2(79) -> 80* a2(151) -> 152* a2(116) -> 117* a2(86) -> 87* a2(76) -> 77* a2(148) -> 149* a2(113) -> 114* a2(88) -> 89* a2(78) -> 79* a2(150) -> 151* a2(115) -> 116* a2(85) -> 86* a2(80) -> 81* b2(75) -> 76* b2(147) -> 148* b2(82) -> 83* b2(109) -> 110* b2(84) -> 85* b2(74) -> 75* b2(146) -> 147* b2(111) -> 112* b2(83) -> 84* b2(73) -> 74* b2(145) -> 146* b2(110) -> 111* f20() -> 2* a3(157) -> 158* a3(122) -> 123* a3(159) -> 160* a3(124) -> 125* a3(161) -> 162* a3(121) -> 122* a3(158) -> 159* a3(123) -> 124* a3(160) -> 161* a3(125) -> 126* a0(5) -> 6* a0(7) -> 8* a0(9) -> 1* a0(6) -> 7* a0(8) -> 9* b3(154) -> 155* b3(119) -> 120* b3(156) -> 157* b3(118) -> 119* b3(155) -> 156* b3(120) -> 121* b0(2) -> 3* b0(4) -> 5* b0(3) -> 4* 1 -> 3,4 6 -> 37* 8 -> 10* 13 -> 82* 15 -> 73* 17 -> 46* 18 -> 5* 41 -> 145* 43 -> 109* 45 -> 12* 54 -> 39* 81 -> 48* 90 -> 75* 113 -> 154* 115 -> 118* 117 -> 83* 126 -> 85* 153 -> 111* 162 -> 120* problem: Qed