#include <stdio.h>
#include <stdlib.h>

int factorial(int x){
	int x_aux = x - 1;
	if (x <= 1){
		return 1;
	}
	else {
		x = x * factorial(x_aux);
	}
	return x;
}

int main(int argc, char* argv[]){
	int x = atoi(argv[1]);
	printf("%d\n", factorial(x));
}