#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int* arr = new int[n];
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  sort(arr, arr + n);
  int min = arr[0], max = arr[n - 1];
  cout << (max - min - (n - 2 + 1)) << endl;
  return 0;
}
