symbolic p(2), n, m;
R  := { [ir,jr] : 1 <= ir <= n && 1 <= jr <= m };
W1 := { [iw,jw] : 1 <= iw <= n && 1 <= jw <= m && p(Set) >= 0 };
W2 := { [iw,jw] : 1 <= iw <= n && 1 <= jw <= m && p(Set) <  0 };
Exposed := R intersection complement ( W1 union W2 );
Exposed;