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