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: Accepted)

using System;
using System.Collections.Generic;
class Program
{
	static void Main(string[] args)
	{
        // マップの作成
        List<string> e1 = new List<string>(){ "A", "T" };
        List<string> e2 = new List<string>(){ "C", "G" };

		// 入力読み込み
        string b = Console.ReadLine();

		// 出力
		string outPut = "";

		// 対応表の確認
		if (e1.Contains(b))
		{
			foreach(string s in e1)
			{
				if (s != b)
				{
					outPut = s;
				}
			}	
		}
		else if (e2.Contains(b))
		{
			foreach(string s in e2)
			{
				if (s != b)
				{
					outPut = s;
				}
			}	
		}

		//出力
		Console.WriteLine(outPut);
	}
}