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;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;

namespace AtCoder {
    class Program {
        static void Main(string[] args) {

            var input = Console.ReadLine();
            switch (input) {
                case "A": Console.WriteLine("T"); break;
                case "C": Console.WriteLine("G"); break;
                case "G": Console.WriteLine("C"); break;
                case "T": Console.WriteLine("A"); break;
            }
        }
    }
}