YES We show the termination of the TRS R: c(b(a(X))) -> a(a(b(b(c(c(X)))))) a(X) -> e() b(X) -> e() c(X) -> e() -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: c#(b(a(X))) -> a#(a(b(b(c(c(X)))))) p2: c#(b(a(X))) -> a#(b(b(c(c(X))))) p3: c#(b(a(X))) -> b#(b(c(c(X)))) p4: c#(b(a(X))) -> b#(c(c(X))) p5: c#(b(a(X))) -> c#(c(X)) p6: c#(b(a(X))) -> c#(X) and R consists of: r1: c(b(a(X))) -> a(a(b(b(c(c(X)))))) r2: a(X) -> e() r3: b(X) -> e() r4: c(X) -> e() The estimated dependency graph contains the following SCCs: {p5, p6} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: c#(b(a(X))) -> c#(c(X)) p2: c#(b(a(X))) -> c#(X) and R consists of: r1: c(b(a(X))) -> a(a(b(b(c(c(X)))))) r2: a(X) -> e() r3: b(X) -> e() r4: c(X) -> e() The set of usable rules consists of r1, r2, r3, r4 Take the reduction pair: lexicographic combination of reduction pairs: 1. max/plus interpretations on natural numbers: c#_A(x1) = max{2, x1} b_A(x1) = x1 + 20 a_A(x1) = max{7, x1 - 17} c_A(x1) = max{1, x1 - 4} e_A = 0 2. max/plus interpretations on natural numbers: c#_A(x1) = 0 b_A(x1) = max{1, x1 - 2} a_A(x1) = 3 c_A(x1) = 4 e_A = 0 The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.