use std::io::{stdin, Read};
use std::str::FromStr;

// https://qiita.com/tubo28/items/e6076e9040da57368845
fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

#[allow(dead_code)]
fn main() {
    let n = read::<usize>();
    let aa = (0..n).map(|_| read::<usize>()).collect::<Vec<_>>();
    let mut a = aa[0];
    for i in 1..n {
        a = lcm(a, aa[i])
    }
    a -= 1;

    let mut ans = 0;
    for i in 0..n {
        ans += a % aa[i]
    }

    println!("{}", ans);

    fn gcd(a: usize, b: usize) -> usize {
        let mut a = a;
        let mut b = b;
        while b != 0 {
            let temp = a % b;
            a = b;
            b = temp;
        }
        a
    }

    fn lcm(a: usize, b: usize) -> usize {
        (a * b) / gcd(a, b)
    }
}
