let () =
  let a, b = read_line () |>
             Str.split (Str.regexp_string " ") |>
             List.map int_of_string |>
             fun lst -> (List.nth lst 0, List.nth lst 1)
  in
  let ans = if a < b then b - 2
            else 2000000000 - b - 1
  in
  print_int ans; print_newline ()