using System;
public class Program
{
public static void Main()
int n=4,b=0,c=0,d,f=0;
//4, 5, 7, 10, 12, 13, 15, 18, 20 ... n
// 1, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3
d = int.Parse(Console.ReadLine());
while(c<d)
n = n + b;
if(f<3)
b += 1;
}
f++;
/*if(f>3 && f>0)
b -= 1;
f--;
*/
Console.Write("{0},", n );
c++;