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