0 QTRS
a(f, 0) → a(s, 0) a(d, 0) → 0 a(d, a(s, x)) → a(s, a(s, a(d, a(p, a(s, x))))) a(f, a(s, x)) → a(d, a(f, a(p, a(s, x)))) a(p, a(s, x)) → x