#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &&v : a) cin >> v;
    a.emplace_back(0);
    sort(a.begin(), a.end());
    ll ans = 0;
    for(int i = 1; i <= n; i++){
        ans += a[i] - a[i - 1] - 1;
    }
    cout << ans << '\n';
}