md5_hash("hello_world",12,"d1f1b13ee233eca000599110b021bce7").
md5_valid("hello_world",12,"d1f1b13ee233eca000599110b021bce7",X) :-
  md5_check("hello",6,"b1946ac92492d2347c6235b4d2611184",X),
  md5_check("world",6,"0f7220a0df94ad88e497ae2fa6c56cdd",X).