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;

class Program
{
    static void Main(string[] args)
    {
        var input = Console.ReadLine().Split(' ');
        var N = int.Parse(input[0]);
        var Q = int.Parse(input[1]);
        var S = Console.ReadLine().ToCharArray();
        
        for (var i = 0; i < Q; i++) {
            var input2 = Console.ReadLine().Split(' ');
            var l = int.Parse(input2[0]);
            var r = int.Parse(input2[1]);
            var cnt = 0;
            if (l == r) continue;
            for (var j = l-1; j < r-1; j++) {
                if (S[j] == 'A' && S[j+1] == 'C') {
                    cnt++;
                  	j++;
                }
            }
            Console.WriteLine(cnt);   
        }
    }
}