#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long temp,next,sum=0;
    
    if(k==1)
        return 1;
    else
        temp = (k*(k-1) +1);
    k+=1;
    next = (k*(k-1) +1);
    while(temp<next){
        sum+=temp;
        temp+=2;
    }
    return sum;
}

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