#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long long int k) {
    long long int a=k*(k-1)+1;
    unsigned long long int  sum=0;
    sum=(k)*(k-1)/2;
    a=sum+k;
    unsigned long long int ans=a*a-sum*sum;
    return ans;
}

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