?- consult('crypto.pro').
%  ../gv.pro compiled 0.01 sec, 2,696 bytes
%  ../combosets.pro compiled 0.00 sec, 7,560 bytes
% crypto.pro compiled 0.01 sec, 18,480 bytes

Yes
?- crypto(3,2,7,K).

No
?- crypto(3,2,6,K).

K = ex(3, *, 2)

Yes
?- crypto(3,2,1,6,K).

K = ex(1, +, ex(3, +, 2))

Yes
?- crypto(3,2,1,6,14,K).

K = ex(6, +, ex(2, *, ex(3, +, 1)))

Yes
?- halt.