using System;
public class Program
{
public static void Main()
int product = 1;
for (int i = 20; i > 1; i--)
if (!ShouldIgnore(i))
product *=i;
}
Console.WriteLine(product);
static private bool ShouldIgnore(int input)
if ((input != i ) && (i%input==0))
return true;
return false;