fn fibonacci_rec(n: u8) -> u64 {
    if n < 2 {
        return n;
    }

    return fibonacci_rec(n - 1) + fibonacci_rec(n - 2);
}

fn fibonacci_iter(n: u8) -> u64 {
    let mut counter = 0;
    let mut a = 0;
    let mut b = 1;

    while counter < n {
        let temp = a + b;
        a = b;
        b = temp;

        counter += 1;
    }

    return a;
}