#define A(x, s) x s x
#define B(x, s) A(x, s) s A(x, s)
#define C(x, s) B(x, s) s B(x, s)
#define D(x, s) C(x, s) s C(x, s)
#define E(x, s) D(x, s) s D(x, s)

int product(int x, int y) {
    int t = 1, p = (-!!(x & 1) & y);
    E(p += (t <<= 1, y <<= 1, -!!(x & t) & y), ;);
    return p;
}