// Ackermann function benchmark - deep recursion
fn ack(m: i64, n: i64) -> i64 {
    if m == 0 { n + 1 }
    else if n == 0 { ack(m - 1, 1) }
    else { ack(m - 1, ack(m, n - 1)) }
}

fn main() {
    let result = ack(3, 10);
    println!("ack(3,10) = {}", result);
}