#include <bits/stdc++.h>
using namespace std;
int n, m, i, j, k, a[10010], ans;
int main() {
  scanf("%d", &n);
  for (i = 1; i <= n; i++) scanf("%d", &a[i]);
  sort(a + 1, a + n + 1);
  for (i = 2; i <= n; i++) ans += a[i] - a[i - 1] - 1;
  printf("%d\n", ans);
  return 0;
}
