TORPAcyc is applied to the string rewriting system a b b -> a a a -> b b b b b a -> a b a Tropical matrix interpretation interpretation of a: / 1 0 \ \ 2 1 / interpretation of b: / 3 0 \ \ 0 1 / remove rule 2 continue with: a b b -> a b b a -> a b a interpretation of a: 0 interpretation of b: 9 remove rule 2 continue with: a b b -> a interpretation of a: 7 interpretation of b: 5 remove rule 1 termination has been proved