/*
1290 獻給杭電五十周年校慶的禮物
Time Limit : 1000 ms  Memory Limit : 32768 K  Output Limit : 256 K  

0 MS 344 KB 135 B 
GUN C++
*/
#include <iostream.h>

int main()
{
    int n;
    while(cin>>n)
    {
		cout<<(n*n*n+5*n+6)/6<<endl;
    }
    return 0;
}