T = gets.to_i
S = T.times.map {gets.chomp}

def f(s, i, r, g, w)
  if i == -1 and r == 0 and g == 0
    "possible"
  elsif (i == -1 and (r > 0 or g > 0)) or
       (s[i] == "G" and r == 0) or (s[i] == "W" and g == 0 and w == 0)
    "impossible"
  elsif s[i] == "R"
    f(s, i - 1, r + 1, g, w)
  elsif s[i] == "G"
    f(s, i - 1, r - 1, g + 1, w)
  else
    f(s, i - 1, r, [g - 1, 0].max, w + 1)
  end
end

ans = S.map {|s| f(s, s.size - 1, 0, 0, 0)}
puts ans