!> This file was processed by `fypp`.
!> Today's fortune: "forever WJ...", really OK?
!> ランダムウォーク猿「'半分全列挙' で はっぴー.」
program f902946
  use, intrinsic :: iso_fortran_env
  !> auto use module
  implicit none
  integer(int32), parameter :: dy(*) = [1, 0, -1, 0]
  integer(int32), parameter :: dx(*) = [0, 1, 0, -1]
  integer(int32) :: h, w
  character, allocatable :: grids(:, :)
  logical, allocatable :: visited(:, :)
  integer(int32) :: i, j
  read(input_unit, *) h, w
  allocate(grids(h, w))
  do i = 1, h
     read(input_unit, '(*(a1))') grids(i, :)
  end do
  allocate(visited(h, w), source = .false.)
  do j = 1, w
     do i = 1, h
        if (visited(i, j)) cycle
          if (grids(i, j) == ".") cycle
        ! write(error_unit, *) j, i, grids(i, j)
        block
          integer(int32) :: cnts
          character :: first_c
          cnts = 0
          call dfs_count(h, w, grids, visited, cnts, i, j)
          if (cnts < 4) cycle
          first_c = grids(i, j)
          call dfs_fill(h, w, first_c, grids, i, j)
        end block
     end do
  end do
  do i = 1, h
     write(output_unit, '(*(a1))') grids(i, :)
  end do
contains
  pure recursive subroutine dfs_count(h, w, grids, visited, cnts, y, x)
    integer(int32), intent(in) :: h, w
    character, intent(in) :: grids(h, w)
    logical, intent(inout) :: visited(h, w)
    integer(int32), intent(inout) :: cnts
    integer(int32), intent(in) :: y, x
    integer(int32) :: d
    if (visited(y, x)) return
    visited(y, x) = .true.
    cnts = cnts + 1
    do d = 1, size(dy)
       associate(ny => y + dy(d), nx => x + dx(d))
         if (ny < 1 .or. ny > h .or. nx < 1 .or. nx > w) cycle
         if (visited(ny, nx)) cycle
         if (grids(y, x) /= grids(ny, nx)) cycle
         call dfs_count(h, w, grids, visited, cnts, ny, nx)
       end associate
    end do
  end subroutine dfs_count
  pure recursive subroutine dfs_fill(h, w, c, grids, y, x)
    integer(int32), intent(in) :: h, w
    character, intent(in) :: c
    character, intent(inout) :: grids(h, w)
    integer(int32), intent(in) :: y, x
    integer(int32) :: d
    grids(y, x) = "."
    do d = 1, size(dy)
       associate(ny => y + dy(d), nx => x + dx(d))
         if (ny < 1 .or. ny > h .or. nx < 1 .or. nx > w) cycle
         if (c /= grids(ny, nx)) cycle
         call dfs_fill(h, w, c, grids, ny, nx)
       end associate
    end do
  end subroutine dfs_fill
end program f902946