#include <iostream>

#define PROMPT "Please enter a whole number: "
#define NOT_PRIME "The number is not a prime number.\n"
#define PRIME "The number is a prime number.\n"        
#define DONE 0          /* ends successful program */                           
#define FIRST_FACTOR 2  /* initial value in for loop */                         

using namespace std;
//using std::cout;
//using std::cin;

int main(){
   int i;       /* loop counter */
   int number; /* number provided by user */

   cout << PROMPT;  /* promt user */
   cin >> number;  /* wait for user input */

   /* Prime numbers are defined as any number 
    * greater than one that is only divisible
    * by one and itself. Dividing the number
    * by two shortens the time it takes to
    * complete. */

   for(i = FIRST_FACTOR; i < number/2 +1; ++i)
   {
      //cout << number << " " << number%i << endl;

      if(number%i == 0)
      {    /* if divisible */
	 cout << NOT_PRIME << number << endl; /* not prime */
	 return DONE;        /* exit program */
      }
   }

   /* if number is not divisible by anything
    * than it must be prime */
   cout << PRIME << number << endl;

   return 0;     /* exit program */
}