#include <bits/stdc++.h>

using namespace std;

unsigned long long sumOfGroup(int k) {
    long long n = (long long )k * (k -1 )/2;    
    long long n2 = (long long )k * (k + 1 )/2;    
    long long a = (long long )2*n + 1;    
    long long b = (long long )2*n2 - 1;        
    unsigned long long ans = k * (a+b) / 2;
    return ans;
    
}

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