[백준] 10872번

import java.util.Scanner;

public class Main {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);

      int N = sc.nextInt();
      int ans = 1;

      if (N == 0) {    // 입력값이 0인 경우
         System.out.println(1);
      } else {
         for (int i = 1; i <= N; i++) {
            ans *= i;
         }
         System.out.println(ans);
      }
   }
}