fn main() {
    let v = read_vec::<usize>();
    let (n, k) = (v[0], v[1] as i64);
    let a = read_vec::<i64>();
    let sum_a = a.iter().sum::<i64>();

    let mut ans = 0;
    for anum in a {
        ans *= k;
        ans += anum;
        ans %= sum_a;
    }
    println!("{}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}