#include <bits/stdc++.h>
#include<vector>
using namespace std;

long sumOfGroup(int k) {
    long value =(2*k)-1;
    long  a[1000000];
    long sum=0;
    int m=1;
    a[0]=value;
    for(int i=1;i<=k;i++)
    {    a[m]=a[m-1]+2;
         m++;
         sum+=a[i];       
    }
    
    
    return sum;
}

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