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

int main(int argc, char *argv[])
{
    long double dfac;
    long long ifac, i, n;

    if (argc != 2) {
	fprintf(stderr, "usage: fact n\n");
	exit(1);
    }
    
    n = atoi(argv[1]);
    if (n < 0) {
	fprintf(stderr, "n must be nonnegative\n");
	exit(1);
    }

    ifac = 1;
    dfac = 1.0;
    for (i = 1; i <= n; i++) {
	ifac = i * ifac;
	dfac = i * dfac;
    }

    printf("ifac = %lld, dfac = %Lf\n", ifac, dfac);
    return 0;
}