Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120
import java.io.*;

class Main{
public static void main(String[] args) throws IOException{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String str;
while((str=br.readLine())!=null){
int x=Integer.parseInt(str);
System.out.println(fact(x));
}
}
private static long fact(int x){
if(x==0){return 1;}
return x*fact(x-1);
}
}