#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long sum=0;
     int n=1,i;
     for(i=1;i<=k;i++)
     {
       sum+=(3*(k-1))+n;
       n+=2;
     }
     return sum;
}

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