YES We show the termination of the TRS R: f(s(x),y) -> f(x,s(x)) f(x,s(y)) -> f(y,x) f(c(x),y) -> f(x,s(x)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(x)) p2: f#(x,s(y)) -> f#(y,x) p3: f#(c(x),y) -> f#(x,s(x)) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) r3: f(c(x),y) -> f(x,s(x)) The estimated dependency graph contains the following SCCs: {p1, p2, p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(x)) p2: f#(c(x),y) -> f#(x,s(x)) p3: f#(x,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) r3: f(c(x),y) -> f(x,s(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, x2 - 1} s_A(x1) = x1 + 1 c_A(x1) = x1 The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(c(x),y) -> f#(x,s(x)) p2: f#(x,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) r3: f(c(x),y) -> f(x,s(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#(c(x),y) -> f#(x,s(x)) p2: f#(x,s(y)) -> f#(y,x) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) r3: f(c(x),y) -> f(x,s(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} c_A(x1) = max{2, x1 + 1} s_A(x1) = max{3, x1 + 2} 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#(c(x),y) -> f#(x,s(x)) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) r3: f(c(x),y) -> f(x,s(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#(c(x),y) -> f#(x,s(x)) and R consists of: r1: f(s(x),y) -> f(x,s(x)) r2: f(x,s(y)) -> f(y,x) r3: f(c(x),y) -> f(x,s(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{2, x1, x2} c_A(x1) = x1 + 3 s_A(x1) = max{1, x1} The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.