{
  read N
; write @N
; if @N <= 0 || 0 != @N%%1 then 
    write " is not a positive integer"
  else if 1 == @N then 
    write " is 1" 
  else 
    {
      2 ~> I
    ; while 0 != @N%%@I && @I*@I < @N do
        @I+1 ~> I
    ; if @N%%@I == 0 && @I < @N then 
        {
          write " has prime factor "
        ; write @I
        }
      else write " is prime!"
    }
; write
}