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

int main()
{
    FILE *factorialin = NULL, *factorialout = NULL;
    int x = 0;
    factorialin = fopen("factorial.in","r");

    fscanf(factorialin,"%d",&x);

    fclose(factorialin);


    factorialout = fopen("factorial.out","w");

    fprintf(factorialout,"%d",factorial(x));

    fclose(factorialout);


}

int factorial (int n)
{
    if (n <= 0) return 1;
	if (n==1) return 1;
	else return n*factorial(n-1);
}