:- use_module(library(clpfd)).

strictly_ascending([]).
strictly_ascending([S|Ss]) :-
        strictly_ascending_(Ss, S),
        strictly_ascending(Ss).

strictly_ascending_([], _).
strictly_ascending_([A|_], S) :- A #> S.

%?- strictly_ascending(As), As ins 0..5, label(As).

mstd(Set) :-
        findall(S, (member(A, Set), member(B, Set), S is A + B), Sums),
        findall(D, (member(A, Set), member(B, Set), D is A - B), Diffs),
        sort(Sums, SSums), sort(Diffs, SDiffs),
        length(SSums, LS), length(SDiffs, LD),
        LS > LD.

sumdiff(N, Ls) :-
        length(Ls, N),
        between(0, inf, Limit),
        Ls ins 0..Limit,
        strictly_ascending(Ls),
        label(Ls),
        mstd(Ls),
        !.

%?- mstd([0,2,3,4,7,11,12,14]).
%?- Sums = [2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 25, 26], length(Sums, L).
%?- Diffs = [-14, -12, -11, -10, -9, -8, -7, -5, -4, -3, -2, -1, 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 14], length(Diffs, L).

%?- sumdiff(8, L).


%?- mstd([0,1,2]).

%?- mstd([0,14]).