import java.util.*;

public class FunctionExercise5 {
  static Scanner scanner = new Scanner(System.in);

  public static void main(String args[]) {
    int x = 0;
    System.out.print("Please enter a number : ");
    x = scanner.nextInt();
    System.out.println("" + x + "! = " + Fact(x));
  }

  public static int Fact(int p1) {
    int RetVal = 0;
    if (p1 > 0) {
      RetVal = Fact(p1 - 1) * p1;
    } else {
      RetVal = 1;
    }
    return RetVal;
  }
}