csp(C1, C2, C3, C4, C5) :-
    member(C1, [c]),
    member(C2, [b]),
    member(C3, [a,c]),
    member(C4, [a,c]),
    member(C5, [b,c]),
    dif(C1, C2),
    dif(C2, C3),
    dif(C2, C4),
    dif(C3, C4),
    dif(C3, C5),
    dif(C4, C5).

:- use_module(library(clpfd)).

csp(A, B, C, D) :-
    between(0,1, A),
    between(0,3, B),
    between(0,3, C),
    between(0,6, D),
    A #==> B #=< 2,
    C #< 2 #==> A,
    B + C #< 4,
    B #> D,
    D #= 2 * C.