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 Go (1.6) (judge verdict: Accepted)

package main
import (
	"bufio"
	"os"
	"fmt"
)

func main(){
	stdin := bufio.NewScanner(os.Stdin)
	var i,o string
	if stdin.Scan(){
		i = stdin.Text()
	}
	switch i {
	case "A":
		o = "T"
	case "T":
		o = "A"
	case "C":
		o = "G"
	case "G":
		o = "C"
	default:
		o = "Unexpected rune"
	}

	fmt.Println(o)
}