#include <bits/stdc++.h>
using namespace std;
void optimize() {
  ios_base::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
}
int main() {
  int n, ans = 0;
  cin >> n;
  int arr[n];
  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] + 1) {
      ans += arr[i] - arr[i - 1] - 1;
    }
  }
  cout << ans;
}
