:- lib(ic).
sendmore(Digits) :-
    Digits = [S,E,N,D,M,O,R,Y],
% Assign a finite domain with each letter - S, E, N, D, M, O, R, Y - 
% in the list Digits
    Digits :: [0..9],
% Constraints
    alldifferent(Digits),
    S #\= 0,
    M #\= 0,
                 1000*S + 100*E + 10*N + D
               + 1000*M + 100*O + 10*R + E
    #= 10000*M + 1000*O + 100*N + 10*E + Y,
% Search
    labeling(Digits).