Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of uppercase English letters. Find the length of the longest ACGT string that is a substring (see Notes) of S.

Here, a ACGT string is a string that contains no characters other than A, C, G and T.

Notes

A substring of a string T is a string obtained by removing zero or more characters from the beginning and the end of T.

For example, the substrings of ATCODER include TCO, AT, CODER, ATCODER and (the empty string), but not AC.

Constraints

S is a string of length between 1 and 10 (inclusive).

Each character in S is an uppercase English letter.

Input

Input is given from Standard Input in the following format:

S

Output

Print the length of the longest ACGT string that is a substring of S.

Sample Input 1

ATCODER

Sample Output 1

3

Among the ACGT strings that are substrings of ATCODER, the longest one is ATC.

Sample Input 2

HATAGAYA

Sample Output 2

5

Among the ACGT strings that are substrings of HATAGAYA, the longest one is ATAGA.

Sample Input 3

SHINJUKU

Sample Output 3

0

Among the ACGT strings that are substrings of SHINJUKU, the longest one is (the empty string).

Solution in OCaml (4.02.3) (judge verdict: Accepted)

open Printf
open Scanf

let (++) = Int64.add
let (--) = Int64.sub
let ( ** ) = Int64.mul
let (//) = Int64.div
let (%%) = Int64.rem
let landl = Int64.logand
let lorl = Int64.logor
let lnotl = Int64.lognot
let lxorl = Int64.logxor
let lsll = Int64.shift_left
let lsrl = Int64.shift_right_logical
let long = Int64.of_int
let succl = Int64.succ
let predl = Int64.pred

let read_int _ = scanf " %d " (fun x -> x)
let read_long _ = scanf " %Ld " (fun x -> x)
let read_str _ = scanf " %s " (fun x -> x)
let read_double _ = scanf " %f " (fun x -> x)

let m = 1_000_000_007L

let rec gcd a b = if b = 0L then a else gcd b (a %% b)

let rec mod_pow a = function
  | 0L -> 1L
  | b -> (if b %% 2L = 0L then 1L else a) ** mod_pow (a ** a %% m) (b//2L) %% m

let explode s =
  let rec exp i l =
    if i < 0 then l else exp (i - 1) (s.[i] :: l) in
  exp (String.length s - 1) []

let rec max_len m accum = function
  | [] -> max m accum
  | c :: rest when c = 'A' || c = 'C' || c = 'G' || c = 'T' ->
    max_len m (accum+1) rest
  | _ :: rest -> max_len (max m accum) 0 rest

let () =
  let s = read_str () in
  printf "%d\n" (max_len 0 0 @@ explode s)