/**
 * @author Daniel "3ICE" Berezvai
 */
public class Fact {
	public static void main(String[] args) {
		if(args.length!=1){
			System.out.println("Hello, please give me an integer as a command line argument.");
		}else{
			int a=Integer.parseInt(args[0]);
			int f = 1;
			for(int i=1; i<=a; i++){
				f = f*i;
			}
			if(a<0){
				System.out.println("Sorry, I don't know what to do with negative numbers.");
			}else{
				System.out.println("Factorial of " + a + " = " + f);
			}
		}
	}
}