consMarked_femptyfMarked_ggkxdaf(a,empty)g(a,empty)f(a,cons(x,k))f(cons(x,a),k)g(empty,d)dg(cons(x,k),d)g(k,cons(x,d))f(a,empty)g(a,empty)f(a,cons(x,k))f(cons(x,a),k)g(empty,d)dg(cons(x,k),d)g(k,cons(x,d))Marked_f(a,empty)Marked_g(a,empty)Marked_f(a,cons(x,k))Marked_f(cons(x,a),k)Marked_g(cons(x,k),d)Marked_g(k,cons(x,d))f(a,empty)g(a,empty)f(a,cons(x,k))f(cons(x,a),k)g(empty,d)dg(cons(x,k),d)g(k,cons(x,d))Marked_f(a,cons(x,k))Marked_f(cons(x,a),k)Marked_f2Marked_f(a,cons(x,k))Marked_f(cons(x,a),k)f(a,empty)g(a,empty)f(a,cons(x,k))f(cons(x,a),k)g(empty,d)dg(cons(x,k),d)g(k,cons(x,d))f(a,empty)g(a,empty)f(a,cons(x,k))f(cons(x,a),k)g(empty,d)dg(cons(x,k),d)g(k,cons(x,d))Marked_g(cons(x,k),d)Marked_g(k,cons(x,d))Marked_g1Marked_g(cons(x,k),d)Marked_g(k,cons(x,d))f(a,empty)g(a,empty)f(a,cons(x,k))f(cons(x,a),k)g(empty,d)dg(cons(x,k),d)g(k,cons(x,d))