Problem:
Score : 100 points

Problem Statement

On the Planet AtCoder, there are four types of bases: A, C, G and T. A bonds with T, and C bonds with G.

You are given a letter b as input, which is A, C, G or T. Write a program that prints the letter representing the base that bonds with the base b.

Constraints

b is one of the letters A, C, G and T.

Input

Input is given from Standard Input in the following format:

b

Output

Print the letter representing the base that bonds with the base b.

Sample Input 1

A

Sample Output 1

T

Sample Input 2

G

Sample Output 2

C

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCorder
{
    class Program
    {
        static int H = 0;
        static int W = 0;

        static void Main(string[] args)
        {
            var strList = new List<char> { 'A', 'T', 'C', 'G' };
            string in1 = Console.ReadLine();

            var result = 0;
            var count = 0;

            foreach (char c in in1)
            {
                if (strList.Any(x => x == c))
                {
                    count++;
                }
                else
                {
                    if (count >= result)
                    {
                        result = count;
                    }
                    count = 0;
                }
            }

            if (count == in1.Length)
            {
                result = count;
            }

            Console.WriteLine(result.ToString());
        }
    }
}