#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[1000], count = 0;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (int i = 0; i < n - 1; i++) {
    count = count + (a[i + 1] - a[i] - 1);
  }
  cout << count;
  return 0;
}
