#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    long  long q= (k*(k-1))/2;
    q=q*2-1;
    q=q+2;
    //cout<<"q is...."<<q<<endl;
    int j=1;
    long long sum=0;
    while(j<=k)
    {
        sum=sum+q;
        q=q+2;
        ++j;
    }
    return sum;
}

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