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.Linq;

namespace abc122
{
    class A
    {
        static void Main(string[] args)
        {
            char res = 'A';
            switch (Input.Char()) {
                case 'A':
                    res = 'T';
                    break;
                case 'T':
                    res = 'A';
                    break;
                case 'C':
                    res = 'G';
                    break;
                case 'G':
                    res = 'C';
                    break;
            }
            Console.WriteLine(res);

        }

        /** Input Class */
        internal static class Input
        {
            /** input int */
            public static int Int() => int.Parse(Console.ReadLine());

            /** input str */
            public static string Str() => Console.ReadLine();

            /** input array of int */
            public static int[] IntArray() => Console.ReadLine().Split(' ').Select(int.Parse).ToArray();

            /** input array of string */
            public static string[] StrArray() => Input.Str().Split(' ');

            /** input array of char */
            public static char[] CharArray() => Input.Str().ToCharArray();

            public static char Char() => Input.CharArray().First();
        }
    }
}