program yukicoder_2492
  use, intrinsic :: iso_fortran_env
  implicit none
  integer(int32) :: n, w
  integer(int32), allocatable :: vs(:), ws(:), ws_le_idx(:)
  integer(int32) :: i
  read(input_unit, *) n, w
  allocate(vs(n), ws(n))
  do i = 1, n
     read(input_unit, *) vs(i), ws(i)
  end do
  ws_le_idx = pack([(i, i = 1, n)], ws(:) <= w)
  if (size(ws_le_idx) == 0) then
     write(output_unit, '(i0)') -1
  else
     write(output_unit, '(i0)') maxval(vs(ws_le_idx))
  end if
end program yukicoder_2492