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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;

namespace Contest
{
    class Program
    {
        static void Main(string[] args)
        {
            ABC122.B();
        }

        class ABC122
        {
            public static void A()
            {
                switch (Read.Str())
                {
                    case "A": Console.WriteLine("T"); return;
                    case "T": Console.WriteLine("A"); return;
                    case "G": Console.WriteLine("C"); return;
                    case "C": Console.WriteLine("G"); return;
                }
            }
            public static void B()
            {
                var S = Read.Str();
                var hash = new HashSet<char>(new char[] { 'A', 'C', 'G', 'T' });
                int longest = 0;
                int current = 0;
                foreach(var c in S)
                {
                    if (hash.Contains(c))
                    {
                        current++;
                        longest = Math.Max(longest, current);
                    }
                    else
                    {
                        current = 0;
                    }
                }
                Console.WriteLine(longest);
            }
            public static void C()
            {
                var N = Read.Int();
                var Q = Read.Int();
                var S = Read.Str();
                var LR = Read.TupleInt(Q);


                var BIT = new Util.BIT(N);
                for(int i = 0; i < N - 1; ++i)
                {
                    if(S[i]=='A' && S[i + 1] == 'C') { BIT.Add(i + 1, 1); }
                }
                foreach(var lr in LR)
                {
                    Console.WriteLine(BIT.Sum(lr.Item2 - 1) - BIT.Sum(lr.Item1 - 1));
                }
            }
            public static void D()
            {
                var N = Read.Int();

                var ACGT = new string[] { "A", "C", "G", "T" };
                var dp = new long[64, N + 1];
                for(int i = 0; i < 64; ++i)
                {
                    var str = ACGT[i / 16] + ACGT[(i % 16) / 4] + ACGT[i % 4];
                    dp[i, 3] = (str == "AGC" || str == "GAC" || str == "ACG") ? 0 : 1;
                }
                for(int j = 4; j <= N; ++j)
                {
                    for (int i = 0; i < 64; ++i)
                    {
                        var v1 = ACGT[i / 16];
                        var v2 = ACGT[(i % 16) / 4];
                        var v3 = ACGT[i % 4];

                        bool[] NG = new bool[4];

                        if (v2 == "A" && v3 == "C")
                        {
                            NG[2] = true;
                        }
                        if (v3 == "G" && (v1 == "A" || v2 == "A"))
                        {
                            NG[1] = true;
                        }
                        if (v2 == "G" && (v1 == "A" || v3 == "A"))
                        {
                            NG[1] = true;
                        }
                        for(int k = 0; k < 4; ++k)
                        {
                            if (!NG[k])
                            {
                                var target = (i % 16) * 4 + k;
                                dp[target, j] = (dp[target, j] + dp[i, j - 1]) % Util.P;
                            }
                        }
                    }
                }
                long total = Enumerable.Range(0, 64).Select(i => dp[i, N]).Sum() % Util.P;
                Console.WriteLine(total);
            }
        }
        class Util
        {
            public static readonly long P = 1000000007;
            public class BIT
            {
                int N; long[] array;
                public BIT(int m) { for (int n = 1; ; n *= 2) { if (n >= m) { N = n; array = new long[N + 1]; break; } } }
                public void Add(int idx, int v) { for (int x = idx; x <= N; x += x & -x) { array[x] += v; } }
                public long Sum(int idx) { long ret = 0; for (int x = idx; x > 0; x -= x & -x) { ret += array[x]; } return ret; }
            }

        }

        static class Read
        {
            static Queue<string> queue = new Queue<string>();
            static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
            public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
            public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
            public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
            public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
            public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
            public static string[] StrN() { return Console.ReadLine().Split(' '); }
            public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
            public static long[,] LongMatrix(int r, int c)
            {
                var mat = new long[r, c];
                for (int i = 0; i < r; ++i)
                {
                    var x = Read.LongN();
                    for (int j = 0; j < c; ++j)
                    {
                        mat[i, j] = x[j];
                    }
                }
                return mat;
            }
            public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M)
            {
                Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
                for (int i = 0; i <= N; ++i)
                {
                    dict.Add(i, new HashSet<int>());
                }
                for (int i = 0; i < M; ++i)
                {
                    var ab = Read.IntN();
                    dict[ab[0]].Add(ab[1]);
                    dict[ab[1]].Add(ab[0]);
                }
                return dict;
            }
        }
    }
}