fn main() -> i64 {
    let mut x: i64 = 10;
    x += 5;
    print_i64(x);   // 15
    x -= 3;
    print_i64(x);   // 12
    x *= 2;
    print_i64(x);   // 24
    x /= 4;
    print_i64(x);   // 6
    return 0;
}