import java.util.Scanner;

public class factorialV4 {


    public static double factorial(int n) {
	double factorial = 1;

	for (int i = 2; i <= n; i++)
	    factorial *= i;

	return factorial;
    }

    public static void main (String[] args) {

	Scanner entrada  = new Scanner (System.in);
	int numero;

	do {
	    System.out.print("Dime un numero entero no negativo: ");
	    numero = entrada.nextInt();
	} while (numero < 0);
	
	System.out.println("El factorial de " + numero + " vale " + factorial(numero));
	
    }

}