let h, w, c = Scanf.scanf " %d %d" @@ fun a b -> a, b, ref 0
let a_ss = Array.(init h @@ fun _ -> init w @@ fun _ -> Scanf.scanf " %c" @@ fun a -> if a = '#' then incr c; a)
let rec f i y x = if i >= h + w - 2 then (if y = h - 1 && x = w - 1 then (print_endline "Possible"; exit 0))
  else (if x + 1 < w && a_ss.(y).(x + 1) = '#' then f (i + 1) y (x + 1); if y + 1 < h && a_ss.(y + 1).(x) = '#' then f (i + 1) (y + 1) x)
let _ = if !c = h + w - 1 then f 0 0 0; print_endline "Impossible"