#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];
  }
  sort(a, a + n);
  int count = 0;
  if (n == 1) {
    cout << "0" << endl;
    return 0;
  }
  for (int i = 1; i < n; i++) {
    count += (a[i] - a[i - 1]) - 1;
  }
  cout << count << endl;
}
