% Berechnen der Fakultät

fak(0,1).
fak(N,R) :-  N > 0,  M is N - 1,  fak(M,R1),  R is N * R1.

?- fak(6,N).

solve(A, B, C, D, E, F, G, H, I) :-
  (
    between(1,9,A),
    between(1,9,B), B =\= A,
    between(1,9,C), C =\= B, C =\= A,
    between(1,9,D), D =\= C, D =\= B, D =\= A,
    between(1,9,E), E =\= D, E =\= C, E =\= B, E =\= A,
    between(1,9,F), F =\= E, F =\= D, F =\= C, F =\= B, F =\= A,
    between(1,9,G), G =\= F, G =\= E, G =\= D, G =\= C, G =\= B, G =\= A,
    between(1,9,H), H =\= G, H =\= F, H =\= E, H =\= D, H =\= C, H =\= B, H =\= A,
    between(1,9,I), I =\= H, I =\= G, I =\= F, I =\= E, I =\= D, I =\= C, I =\= B, I =\= A,
    A + B + G =:= 15,
    C + D + H =:= 15,
    E + F + I =:= 15,
    G + H + I =:= 15,

    A + B + C + D + E + F =:= 30
  ).


/* 
  Call it from the Prolog command prompt as follows:

   ?- solve(A, B, C, D, E, F, G, H, I).
*/

?- write('Hello World'), nl.