#include <bits/stdc++.h>
using namespace std;
const int MX = (int)1e6 + 17;
const int MOD = (int)1e9 + 7;
const long long LINF = (long long)1e18 + 7;
const int INF = (int)999999999;
inline long long IN() {
  long long x = 0, ch = getchar(), f = 1;
  while (!isdigit(ch) && (ch != '-') && (ch != EOF)) ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 1) + (x << 3) + ch - '0';
    ch = getchar();
  }
  return x * f;
}
inline void OUT(long long x) {
  if (x < 0) putchar('-'), x = -x;
  if (x >= 10)
    OUT(x / 10), putchar(x % 10 + '0');
  else
    putchar(x + '0');
}
int n, x, ans;
int a[3001];
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + 1 + n);
  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;
  return 0;
}
