YES We show the termination of the TRS R: f(s(x),y) -> f(x,s(s(x))) f(x,s(s(y))) -> f(y,x) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(s(x))) p2: f#(x,s(s(y))) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(s(x))) r2: f(x,s(s(y))) -> f(y,x) The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(s(x))) p2: f#(x,s(s(y))) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(s(x))) r2: f(x,s(s(y))) -> f(y,x) The set of usable rules consists of (no rules) Take the reduction pair: max/plus interpretations on natural numbers: f#_A(x1,x2) = max{x1 + 2, x2 + 1} s_A(x1) = x1 + 1 The next rules are strictly ordered: p2 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(s(x))) and R consists of: r1: f(s(x),y) -> f(x,s(s(x))) r2: f(x,s(s(y))) -> f(y,x) The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(s(x))) and R consists of: r1: f(s(x),y) -> f(x,s(s(x))) r2: f(x,s(s(y))) -> f(y,x) The set of usable rules consists of (no rules) Take the reduction pair: max/plus interpretations on natural numbers: f#_A(x1,x2) = max{4, x1, x2 - 4} s_A(x1) = max{5, x1 + 2} The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.