YES We show the termination of the TRS R: p(a(x0),p(b(x1),p(a(x2),x3))) -> p(x2,p(a(a(x0)),p(b(x1),x3))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(x2,p(a(a(x0)),p(b(x1),x3))) p2: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(a(a(x0)),p(b(x1),x3)) p3: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(b(x1),x3) and R consists of: r1: p(a(x0),p(b(x1),p(a(x2),x3))) -> p(x2,p(a(a(x0)),p(b(x1),x3))) The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(a(a(x0)),p(b(x1),x3)) and R consists of: r1: p(a(x0),p(b(x1),p(a(x2),x3))) -> p(x2,p(a(a(x0)),p(b(x1),x3))) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: p#_A(x1,x2) = max{x1 + 5, x2 + 10} a_A(x1) = max{4, x1} p_A(x1,x2) = max{x1 + 3, x2 + 5} b_A(x1) = 1 precedence: p# = a = p = b partial status: pi(p#) = [2] pi(a) = [1] pi(p) = [1, 2] pi(b) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: p#_A(x1,x2) = max{4, x2 - 7} a_A(x1) = x1 + 6 p_A(x1,x2) = max{14, x1 + 8, x2 + 3} b_A(x1) = 5 precedence: p# = a = p = b partial status: pi(p#) = [] pi(a) = [1] pi(p) = [] pi(b) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.