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 Ruby (2.3.3) (judge verdict: Wrong Answer)

Input = gets.chomp

def calc(str,prev)
  	cnt = 0
	str.chars{|c| c.match(/[ATCG]/) ? cnt +=1 : break}
    cnt = [prev, str.length < 1 ? cnt : calc(str.split("").drop(1).join, cnt)].max
end

puts calc(Input,0)