9-2

#include<iostream.h>
#include<math.h>

// adad az voroodi migira, elam mikonad
// avval ast yaa na
void main (void)
{
	int adad, i;
	int tedadBakhshPazir=0;

	cout << "yek adad sahih vared konid:";
	cin >> adad;

	i = 2;
	while (i<=sqrt(adad)) {
		if (adad%i == 0) {
			tedadBakhshPazir++;
		}
		i++;
	}

	cout << "adad avval ";
	if (tedadBakhshPazir==0)
		cout << "hast." << endl;
	else cout << "nist." << endl;

}

/*
i=1..n, adad%i==0  ++k   ==>  k==2
i=2..sqrt(n)+1 ==> k==0
i=2..sqrt(n)+1 if (n%i==0) exit
i=2..sqrt(n)+1 if (n%i==0) i=n+1
*/