  program atcoder
  implicit none
  real K, A, B, X, Y
  read *, K
  read *, A, B
  X=int(B/K)
  Y=int(A/K)
   if (X-Y >= 1) then
    print *, 'OK'
   else if (Y-A/K >= 0) then
    print *, 'OK'
   else 
    print *, 'NG'
   end if
  end program atcoder