let () =
    let h, t = Scanf.scanf "%2d:%2d\n" (fun a b -> a, b) in 
    let tt, b = if t < 55 then t+5, false else t+5-60, true in 
    let hh = if b && h < 23 then h+1 else if b then 0 else h in
    let ts = if tt < 10 then "0" ^ string_of_int tt else string_of_int tt in
    let hs = if hh < 10 then "0" ^ string_of_int hh else string_of_int hh in 
    Printf.printf "%s:%s\n" hs ts