// Read a positive integer n and decide if it's prime.
#include <iostream>
using namespace std;
int main()
{
	int n, i, count;
	bool b = true;
	cout << "Enter a positive integer: ";
	cin >> n;
	if (n < 2)
		cout << "Invalid number.\n";
	else if (n == 2)
		cout << "It's prime\n";
	else
	{
		i = 2;
		while (i < n)
		{
			if (n % i == 0)
			{
				b = false;
				break; // quit the loop
			}
			i++;
		}
		if (b)
			cout << "It's prime\n";
		else
			cout << "It is not prime\n";
	}
	
	return 0;
}