#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long temp=0;
    for(int i=1;i<k;i++){
        temp += i*2;
    }
    //cout<<temp<<endl;
    temp +=1;
    //cout<<temp<<endl;
    long ans=0;
    for(int j=0;j<k;j++){
        //cout<<"In";
        ans += temp;
        temp +=2;
    }
    return ans;
}

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