#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long val = (long)k*(k-1)+1;
    int counter = 0;
    long finalValue = 0;
    
    while(counter<k){
        finalValue += val;
        val = val+2;
        ++counter;
    }
    return finalValue;
}

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