#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(unsigned long long k) {
    // Return the sum of the elements of the k'th group.
    
    unsigned long long num = 0;
    
    for(int ar0 = 1; ar0 < k; ar0++) {
        num += ar0;
    }
    
    unsigned long long start = 1 + num*2;
    
    unsigned long long ans = start*k + k*(k-1);
    
    return ans;
}

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