#include <bits/stdc++.h>

using namespace std;

unsigned long long int sumOfGroup(unsigned long long int k) {
    // Return the sum of the elements of the k'th group.
    if(k ==1)
        return 1;
     unsigned long long int numPreviousOdd = k*(k-1)/2;
     unsigned long long int  start = 1 + numPreviousOdd * 2;
     unsigned long long int ans = start;
    for( int i =2; i <= k; i++)
    {
        //cout << start << " , start + 2 = " << start +2 << endl;
        ans += start +2;
        start += 2;
    }
        
    return ans;
}

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