#include <bits/stdc++.h>
using namespace std;
int sumPrevious(int k)
{
    int sum = 0;
    for(int i = 1; i <= k; i++){
        sum+=i;
    }
    return sum;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int k;
    cin >> k;
    vector<int> odds;
    int len = sumPrevious(k), cn = 1;
    for(auto i = 0; i < len; i++){
        odds.push_back(cn);
        cn+=2;
    }
    int sum = 0;
    reverse(odds.begin(), odds.end());
    for(int i = 0; i < k; i++){
        sum+=odds[i];
    }
    cout << sum << endl;
    return 0;
}