#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n;
    cin >> n;
    ll ans = 0;
    for (int i = 0; i <= n; i++) {
        ans += n - i + 1;
    }
    cout << ans << newl;

    return 0;
}