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