sum([],0).

sum([H|T],S) :- sum(T,S2), S is S2+H.

lenggth([], 0).

lenggth([_|T], L) :- lenggth(T, L_T), L is L_T+1.

x_cp(List2, X) :- sum(List2, S), lenggth(List2, L), X is S div L.

getmin([X], X).

getmin([H|Tail], H):- getmin(Tail, TailMin), H < TailMin.

getmin([H|Tail], TailMin):- getmin(Tail, TailMin), TailMin =< H.

first_N([], _, []).

first_N(_, 0, []).

first_N([H|T], N, [H|T1]) :- N2 is N-1, first_N(T, N2, T1).

level1([],_,0).

level1([H|T],X,K) :- H > X, !, level1(T,X,H1_T), K is H1_T + 1.

level1([H|T],X,H1) :- H =< X, level1(T,X,H1).

level2([],_,0).

level2([H|T],X,K) :- H < X, !, level2(T,X,H1_T), K is H1_T + 1.

level2([H|T],X,H1) :- H >= X, level2(T,X,H1).

delta(List1, List2, X, Y) :- level1(List1,X,P1),
level1(List2,X,P2), level2(List1,X,P3),
level2(List2,X,P4),
Y is abs(P1 - P2) + abs(P3 - P4).

delta2([], [], [], _).

delta2(List1, List2, [], X) :- lenggth(List1, L1),
lenggth(List2, L2), L1<L2.

delta2([H1|T1], List2, [H3|T3], X) :- lenggth(List2, L2),
first_N([H1|T1],L2,NewList1), delta(NewList1, List2, X, H3),
delta2(T1, List2, T3, X).