#include <bits/stdc++.h>
using namespace std;
const int MAX = 700000;
const int MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
long long COM(int n, int k) {
  if (n < k) return 0;
  if (n < 0 || k < 0) return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
long long int maxtime(long long int x, long long int y) {
  return (x + y - 1) / y;
}
long long int lcm(long long int number1, long long int number2) {
  long long int m = number1;
  long long int n = number2;
  if (number2 > number1) {
    m = number2;
    n = number1;
  }
  long long int s = -1;
  while (s != 0) {
    s = m % n;
    m = n;
    n = s;
  }
  return m;
}
long long int gcd(long long int number1, long long int number2) {
  long long int m = number1;
  long long int n = number2;
  return m / lcm(m, n) * n;
}
int main() {
  int n;
  cin >> n;
  vector<int> s;
  long long int b = 1;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    b = gcd(b, a);
    s.push_back(a);
  }
  b = b - 1;
  long long int ans = 0;
  for (int i = 0; i < n; i++) {
    ans = ans + b % s[i];
  }
  cout << ans;
}
