YES We show the termination of the TRS R: b(x,y) -> c(a(c(y),a(|0|(),x))) a(y,x) -> y a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: b#(x,y) -> a#(c(y),a(|0|(),x)) p2: b#(x,y) -> a#(|0|(),x) p3: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(a(c(b(|0|(),y)),x),|0|()) p4: a#(y,c(b(a(|0|(),x),|0|()))) -> a#(c(b(|0|(),y)),x) p5: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(|0|(),y) and R consists of: r1: b(x,y) -> c(a(c(y),a(|0|(),x))) r2: a(y,x) -> y r3: a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) The estimated dependency graph contains the following SCCs: {p1, p2, p3, p4, p5} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: b#(x,y) -> a#(c(y),a(|0|(),x)) p2: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(|0|(),y) p3: b#(x,y) -> a#(|0|(),x) p4: a#(y,c(b(a(|0|(),x),|0|()))) -> a#(c(b(|0|(),y)),x) p5: a#(y,c(b(a(|0|(),x),|0|()))) -> b#(a(c(b(|0|(),y)),x),|0|()) and R consists of: r1: b(x,y) -> c(a(c(y),a(|0|(),x))) r2: a(y,x) -> y r3: a(y,c(b(a(|0|(),x),|0|()))) -> b(a(c(b(|0|(),y)),x),|0|()) The set of usable rules consists of r1, r2, r3 Take the reduction pair: lexicographic combination of reduction pairs: 1. max/plus interpretations on natural numbers: b#_A(x1,x2) = max{37, x1 - 7, x2 - 88} a#_A(x1,x2) = max{0, x1 - 87, x2 - 48} c_A(x1) = max{86, x1 - 28} a_A(x1,x2) = max{84, x1 + 1, x2 + 40} |0|_A = 0 b_A(x1,x2) = max{117, x1 + 76, x2 - 54} 2. max/plus interpretations on natural numbers: b#_A(x1,x2) = 0 a#_A(x1,x2) = 1 c_A(x1) = 2 a_A(x1,x2) = 0 |0|_A = 0 b_A(x1,x2) = 1 The next rules are strictly ordered: p1, p2, p3, p4, p5 We remove them from the problem. Then no dependency pair remains.