# coding=utf-8

id = 158
group = 'clp_r'
number = 68
visible = True
facts = None

solution = '''\
memb158(X, [X|_]).
memb158(X, [_|T]) :-
    memb158(X, T).

check158([], _, _).
check158([X/Y | T], R, Xc/Yc) :-
    { (X-Xc)*(X-Xc) + (Y-Yc)*(Y-Yc) =< R*R },
    check158(T, R, Xc/Yc).

center(L, R, Xc/Yc) :-
    memb158(Xc/Yc, L),
    check158(L, R, Xc/Yc).
'''