#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long top = ((long)k*(k+1))/2;
    long bottom = ((long)(k-1)*k)/2;
    long sum = ((top*(top+1))-top) - ((bottom*(bottom+1))-bottom);
    
    return sum;
}

int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}