#include <bits/stdc++.h>

using namespace std;
int oddno(int x)
{
    return(x*2+1);
}
long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    int i,j,l,f;
    int y;
    int x=0;
    f=0;
    int h[1000];
    j=k;
    for(l=k-1;l>=0;l--)
    {
        f=f+l;
        //cout<<f<<endl;
    }
    for (i=f;i<=(f+k-1);i++)
    {
        //i=i+f;
        y=oddno(i);
       // cout<<y<<endl;
        x=x+y;
    }
    return(x);
}


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