#include <algorithm>
#include <iostream>
#include <map>
#include <vector>
using namespace std;

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int &v : a)
    cin >> v;
  a.push_back(0);
  sort(a.begin(), a.end());
  long long int ans = 0;
  for (int i = a.size() - 1; i > 0; i--) {
    ans += a[i] - a[i - 1] - 1;
  }
  cout << ans << '\n';
}