main() {
    let x: u64;
    let y: u64;
    let z: u64;
    x = 0;
    z = 0;
    while (copy(x) < 3) {
        x = move(x) + 1;
        y = 0;
        while (copy(y) < 7) {
            y = move(y) + 1;
            z = move(z) + 1;
        }
    }
    assert(move(z) == 21, 42);
    return;
}