* Prime program

      integer p,a,i
      read*,a
      
      do
      i=1,a
      
      p=1                

      if ((a.eq.2).or.(a.eq.3)) then
       goto 10
      end if
                       
      do i=2,(int(a**0.5)+2)
       if (mod(a,i).eq.0) then 
        p=0
        goto 10
       end if 
      end do
 
 10   continue
        
      if (p.eq.1) then 
       print *,a,' is prime.'
      else 
       print *,a,' is not prime.'
      end if
      
      end do  
      end