var2 P,Q;
P\Q = {0,4} union {1,2};

pred even(var1 p) =
  ex2 Q: p in Q
    & (all1 q: 
        (0 < q & q <= p) =>
            (q in Q => q - 1 notin Q)
          & (q notin Q => q - 1 in Q))
    & 0 in Q;

var1 x;
var0 A;

A & even(x) & x notin P;
