#include <bits/stdc++.h>

using namespace std;

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

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