#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long int k) {
    // Return the sum of the elements of the k'th group.
    
    long int i,j=0,sum1=0,sum2=0;
    
    for(i=1;i<=k;i++)
    {
        j=j+i;
  
    }
    
    sum1 = j * j;
    j=0;
    
    for(i=1;i<k;i++)
    {
        j=j+i;
  
    }
    sum2 = j * j;
    
    sum1 = sum1 - sum2;
    
    return sum1;
    
    
}

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