#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    /*long sumk_1 = ((k-1)*(2+(k-2)))/2;
    sumk_1++;
    long sum=0;
    for(int i=1;i<=k;i++){
        long ak=1+(sumk_1-1)*2;
        sum+=ak;
        sumk_1++;
    }
    return sum;*/
    long sumk_1 = (k*(2+(k-1)))/2;
    long skk=((sumk_1)*(2+(sumk_1-1)*2))/2;
    long kk=sumk_1-k;
    long sk=((kk)*(2+(kk-1)*2))/2;
     //  cout<<sk<<" "<<skk<<endl;
    return skk-sk;
    
}

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