#include <bits/stdc++.h>

using ll = long long;
using namespace std;

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

    ll n;
    cin >> n;

    int res;
    if (!n)
    {
        res=1;
    }
    else
    {
        res=(n+1)*(n+2)/2;
    }

    printf("%d\n",res);

    return 0;
}