YES We show the termination of the TRS R: f(|0|(),y) -> |0|() f(s(x),y) -> f(f(x,y),y) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x),y) -> f#(f(x,y),y) p2: f#(s(x),y) -> f#(x,y) and R consists of: r1: f(|0|(),y) -> |0|() r2: f(s(x),y) -> f(f(x,y),y) 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#(f(x,y),y) p2: f#(s(x),y) -> f#(x,y) and R consists of: r1: f(|0|(),y) -> |0|() r2: f(s(x),y) -> f(f(x,y),y) The set of usable rules consists of r1, r2 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1,x2) = max{10, x1 + 5} s_A(x1) = max{6, x1} f_A(x1,x2) = 4 |0|_A = 3 precedence: f# = s = f = |0| partial status: pi(f#) = [1] pi(s) = [1] pi(f) = [] pi(|0|) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1,x2) = max{1, x1} s_A(x1) = max{2, x1 + 1} f_A(x1,x2) = 2 |0|_A = 3 precedence: s = |0| > f# = f partial status: pi(f#) = [1] pi(s) = [] pi(f) = [] pi(|0|) = [] The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.