#include <stdio.h>
#include <math.h>
int main()
{
	int i, j, n;
	int primes[1000];	// to indicate booleans

	printf("Enter number (< 1000): ");
	scanf("%d", &n);

	for (i = 0; i < n; i++)
		primes[i] = 1;	// assume all are primes to start with
	primes[0] = 0; primes[1] = 0;	// 0 and 1 are special cases

	for (i = 2; i < (int)(sqrt(n) + 1); i++)
	{
		if (primes[i] == 0)	// no need to re-check a composite number
			continue;
		for (j = i + 1; j < n; j++)
			if ((j % i) == 0) // check for factors
				primes[j] = 0;	// j has a factor and is not a prime
	}

	for (i = 0; i < n; i++)
		if (primes[i] == 1)	// print only primes
			printf("%d ", i);
	printf("\n");
}