import java.io.*;
 
public class Factorial
{
  static int factorial(int n)
  {
    int result;
    if (n < 2) // detect a base case
      result = 1;
    else
      result = n * factorial(n - 1);
    return result;
  } // factorial

  public static void main(String[] argv) throws Exception
  {
    BufferedReader cin;
    cin = new BufferedReader(new InputStreamReader(System.in)); 

    int n;
    System.out.print("Enter n: ");
    n = new Double(cin.readLine()).intValue();

    System.out.println(factorial(n));
  } // main
} // public class