#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 start=(k*(k-1))/2;
    start=2*start+1;
    long long sum=0;
    long long count=0;
    while(true)
    {
        sum+=start;
        start=start+2;
        count++;
        if(count==k) return sum;
    }
}

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