import java.util.Scanner;

public class Factorial {

public static void main(String[] args) {

System.out.println("Program to find factorial of a number\n---");

int num;

Scanner scanner = new Scanner (System.in);

System.out.print("Enter the number: ");

num = scanner.nextInt();

if (num>20 || num< -20) {

System.out.println("Cannot perform factorial for input greater than or lesser than 20.");

end();

}

scanner.close();

if (num<0) {

num = -num;

System.out.println("-"+num+"! = -"+factorial(num));

end();

//For numbers lesser than zero.

}

else {

System.out.println(num+"! = "+factorial(num));

end();

//For numbers greater than or equal to zero.

}

}

private static long factorial(int num) {

long n = num, output = 1;

while (n>0) {

output = output*n;

n-=1;

}

return output;

}

private static void end() {

System.out.println("---\nThe Program has ended.");

System.exit(0);

}

}