题解 | #模数求和#

import java.util.*;
import java.math.BigInteger;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n];
        BigInteger gmd = new BigInteger("1");
        for(int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
            gmd = gmd.multiply(BigInteger.valueOf(arr[i]));
        }
        gmd = gmd.subtract(BigInteger.valueOf(1));
        int ans = 0;
        for(int i = 0; i < n; i++) {
            ans += (gmd.remainder(BigInteger.valueOf(arr[i])).intValue());
        }
        System.out.println(ans);
    }
}