#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long sum1 = 0;
    long j = 1;
    for(int i=1;i<k;i++)
        sum1 = sum1 + i;
    for(int i=0;i<sum1;i++)
        j = j+2;
    long num = j;
    long sum = 0;
    for(int i=0;i<k;i++){
        sum = sum + j;
        j = j+2;}
    return sum;
        
}

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