fn f(x: i64) -> i64 {
    if x % 2 == 0 { -(x)-1 } else { x + 1 }
}

fn main() {
    println!("{}", f(10));
    println!("{}", f(f(10)));
    println!("{}", f(f(-10)));
    println!("{}", f(f(11)));
    println!("{}", f(f(-11)));
}