#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long long int k) {
    // Return the sum of the elements of the k'th group.
    // 1 2 3 4 5 6
    long long int sum = k*(k-1)/2;
    long long int start,end;
    start=sum;
    end = sum+k;
    
    long long int ans = end*(2+1l*(end-1)*2);
    ans-= start*(2+1l*(start-1)*2);
    
    return ans/2;
    
    
}

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