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