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

bool is_prime(size_t number)
{
	if ( number < 2 ) return false;
	if ( number == 2 ) return true;
	if ( number % 2 == 0 ) return false;

	for ( size_t i = 3, last = (size_t)(double)sqrt(number); i <= last; i += 2 )
		if ( number % i == 0 )
			return false;

	return true;
}

int main(int argc, char* argv[])
{
	size_t limit = 0;
	if ( argc >= 2 )
		limit = strtoull(argv[1], NULL, 10);
	else
		return (void)fprintf(stderr, "usage: cntprimes <LIMIT> [WORKERS]\n"), 1;

//	size_t workers = (size_t)sysconf(_SC_NPROCESSORS_ONLN);
//	if ( argc >= 3 )
//		workers = strtoull(argv[2], NULL, 10);

	size_t prime_count = 0;
	for ( size_t current = 2; current <= limit; ++current )
		if ( is_prime(current) )
			++prime_count;

	fprintf(stdout, "%zu primes found between 2 and %zu\n", prime_count, limit);
	return 0;
}