#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int n, m, k;
int a[N];
int main() {
  cin >> n;
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  sort(a + 1, a + n + 1);
  for (int i = 2; i <= n; i++) {
    if (a[i] <= a[i - 1]) {
      ans += (a[i - 1] - a[i] + 1);
      a[i] = a[i - 1] + 1;
    }
  }
  cout << ans << endl;
}
