#include <stdio.h>

int main(){
	int cont, n;
	long long int fat;

	scanf("%d",&n);

	if (n >= 0){
		for(fat=1, cont=1; cont<=n; cont++){
			fat = fat*cont;
	  	}
		printf("%lli\n",fat);
	}else
		printf("Entrada incorreta!\n");
}