1 #include<iostream>
 2 using namespace std;
 3 
 4 int fun(int n)
 5 {
 6     int sum = 0;
 7     for (;n >= 1;n--)
 8     {
 9         sum += (n*n+n) / 2;
10     }
11     return sum;
12 }
13 
14 int main()
15 {
16     int n;
17     while (cin >> n)
18     {
19         cout <<fun(n)<< endl;
20     }
21     return 0;
22 }