#include <iostream>
#include <cstring>
#include <sstream>
#include <cmath>
#include <string>
#include<cstdio>
using namespace std;
long long int f(int a)
{
	
  	if(a==1)
  		return 2;
  	else if(a==2)
  		return 4;
  	else
  		return (a-1)*a+2;
  
}
int main()
{
    int x=10000;
    while(!0)
    {
                cin>>x
		cout<<f(x)<<endl;
    }
    return 0;
}

請問哪裡有遞迴