#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 0;
  cin >> n;
  int arr[n];
  set<int> s;
  for (int i = 0; i < n; i++) cin >> arr[i];
  sort(arr, arr + n);
  for (int i = 1; i < n; i++) {
    if (arr[i] == arr[i - 1]) {
      c++;
      arr[i]++;
    } else if (arr[i] < arr[i - 1]) {
      while (arr[i] <= arr[i - 1]) {
        arr[i]++;
        c++;
      }
    }
  }
  cout << c;
}
