YES We show the termination of the TRS R: f(x,c(y)) -> f(x,s(f(y,y))) f(s(x),y) -> f(x,s(c(y))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,c(y)) -> f#(x,s(f(y,y))) p2: f#(x,c(y)) -> f#(y,y) p3: f#(s(x),y) -> f#(x,s(c(y))) and R consists of: r1: f(x,c(y)) -> f(x,s(f(y,y))) r2: f(s(x),y) -> f(x,s(c(y))) The estimated dependency graph contains the following SCCs: {p2} {p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(x,c(y)) -> f#(y,y) and R consists of: r1: f(x,c(y)) -> f(x,s(f(y,y))) r2: f(s(x),y) -> f(x,s(c(y))) The set of usable rules consists of (no rules) Take the reduction pair: matrix interpretations: carrier: N^1 order: standard order interpretations: f#_A(x1,x2) = x2 c_A(x1) = x1 + 1 The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(x,s(c(y))) and R consists of: r1: f(x,c(y)) -> f(x,s(f(y,y))) r2: f(s(x),y) -> f(x,s(c(y))) The set of usable rules consists of (no rules) Take the reduction pair: matrix interpretations: carrier: N^1 order: standard order interpretations: f#_A(x1,x2) = x1 s_A(x1) = x1 + 1 c_A(x1) = x1 The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.