#include <bits/stdc++.h>
using namespace std;
const int maxn = 1005;
int a[maxn], n, ans;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  sort(a + 1, a + n + 1);
  for (int i = 2; i <= n; i++) ans += a[i] - a[i - 1] - 1;
  printf("%d", ans);
  return 0;
}
