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

int numprimes (int m) {
	int	i, j, n, is_prime, count;

	i = 0;

	/* start trying out prospective primes at 2 */

	count = 0;
	n = 2;
	while (n <= m) {

		/* assume n is prime */

		is_prime = 1;

		/* try to find a value of j that divides n */

		for (j=2; is_prime && (j < n); j++) 
			if (n % j == 0) is_prime = 0;
		n++;
		if (is_prime) count++;
	}
	return count;
}

int main (int argc, char *argv[]) {
	int	n;

	/* if number of arguments not 2, give an error and exit */

	if (argc != 2) {
		fprintf (stderr, "Usage: countprimes \n");
		exit (1);
	}

	/* find out n */

	n = atoi (argv[1]);

	/* print the number of primes */

	printf ("F(%d) = %d\n", n, numprimes (n));
	exit (0);
}