program main
  implicit none
  integer::T,i
  character*1000::S
  read *,T
  do i=1,T
     read *,S
     call analyze(S)
  end do
contains
  subroutine analyze(S)
    integer::j,len,w,g,r,keitou
    character*1000::S

    len = LEN_TRIM(S)
    w = 0
    g = 0
    r = 0
    do j=1,len
       if(S(j:j).eq.'R') then
          r = r + 1
          if(r.gt.g.or.r.gt.w) then
             print '(a)',"impossible"
             return
          end if
       else if(S(j:j).eq.'G') then
          g = g + 1
          if(g.gt.w) then
             print '(a)',"impossible"
             return
          end if
       else
          w = w + 1
       end if
    end do
    if(g.ne.r) then
       print '(a)',"impossible"
       return
    end if
    w = 0
    g = 0
    r = 0
    do j=len,1,-1
       if(S(j:j).eq.'R') then
          r = r + 1
       else if(S(j:j).eq.'G') then
          g = g + 1
          if(r.eq.0) then
             print '(a)',"impossible"
             return
          end if
       else
          w = w + 1
          if(r.eq.0.or.g.eq.0) then
             print '(a)',"impossible"
             return
          end if
       end if
    end do
    print '(a)',"possible"
  end subroutine analyze

end program main