/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	  {
 
          Scanner sc =new Scanner(System.in);
         long x;
         long y=1;
         x=sc.nextInt();
         if(x>=2 && x<=100){
         for(int i=1;i<=x;i++){
             y*=i;
         }
         System.out.println(y);
         }
         else {
         System.out.println("error");
         }
 
	}
}

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