let s = read_line () in
let c = String.get s 0 in
let len = String.length s in
let s2 = String.make len c in
let s2 = if(int_of_string s <= int_of_string s2) then s2 else (
  let c = (int_of_char c)+1 in
  let s2 = String.make len (char_of_int c) in
  s2
)in
Printf.printf "%s\n" s2
