fn main() {
    let v = read_vec::<i64>();
    let (n, x) = (v[0], v[1]);
    let s = read_vec::<i64>();
    let a = s.iter().map(|&e| x - e).collect::<Vec<_>>();
    let ans = a.iter().sum::<i64>() - x;
    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()
}