#include <stdio.h>
#include <math.h>

int main ()
{
  unsigned int num, p;
  
  printf ("Enter a Positive Number: ");
  scanf ("%u", &num);
  
  switch (num) {
    case 0 :
    case 1 :
      printf("%u is NOT a Prime!\n", num);
      break;
    case 2 :
      printf ("%u is a Prime!\n", num);
      break;
    default:
       if ( num % 2 == 0 ) printf ("%u is NOT a Prime!\n", num);
       else {
         for ( p = 3; p <= sqrt(num); p += 2 )
           if ( num % p == 0) break;
         if ( p > sqrt(num) ) printf ("%u is a Prime!\n", num);
         else                 printf ("%u is NOT a Prime!\n", num);
       }
  }

  return 0;
}