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# (.NET Core 3.1.201) (judge verdict: Accepted)

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

namespace AtCoder.ABC
{
	class QuestionA
	{
		public static void Main(string[] args)
		{
			var s = Console.ReadLine();

			var answer = "";

			for(int i = 0; i < s.Length; i++) {
				if(s[i] == 'A') {
					answer += "T";
				} else if(s[i] == 'T') {
					answer += "A";
				} else if (s[i] == 'C') {
					answer += "G";
				} else if (s[i] == 'G') {
					answer += "C";
				}
			}

			Console.WriteLine(answer);
		}
	}
}