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: Runtime Error)

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

namespace Algorithm
{
    class Program
    {
        const string Key = "AC";

        static void Main(string[] args)
        {
            var line = Console.ReadLine().Split().Select(w => int.Parse(w)).ToArray();
            var s = Console.ReadLine().ToCharArray();

            for (var i = 0; i < line[0]-1; i++)
            {
                if (s[i] == 'A' && s[i + 1] == 'C') s[i] = 'a';
            }

            var t = new int[line[0]];

            for (var i = 0; i < line[0]-1; i++)
            {
                if (s[i] == 'a') t[i + 1] = t[i] + 1;
                else t[i + 1] = t[i];
            }

            for (var i = 0; i < line[1]; i++)
            {
                var b = Console.ReadLine().Split().Select(x => int.Parse(x)).ToArray();
                var l = b[0] - 1;
                var r = b[1] - 1;
                Console.WriteLine(t[r] - t[l]);
            }
        }
    }
}