#include<stdio.h>

 long long int factorial(int n) {
     if ( n < 0) {
         return -1;
     }
     if (n == 0 || n==1) {
         return 1;
     } else {
         return n * factorial(n - 1);
     }
}
 int main() {
     int n;
    
     scanf("%d", &n);
     
     long long int result = factorial(n);
     
     if (result == -1) {
         printf("Invalid Input\n");
     } else {
         printf("the factorial of   %lld\n",n,result);
     }
     return 0;
 }