#include <bits/stdc++.h>   using namespace std;   int main() {     int n, s = 0, a[10000] = {0};     cin >> n;     for (int i = 0; i < n; i++) {       int t;       cin >> t;       a[t]++;     }     for (int i = 1; i < 10000; i++) {       if (a[i] > 1) {         a[i + 1] = a[i + 1] + a[i] - 1;         s = s + a[i] - 1;       }     }     cout << s;     return 0;   }   