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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <numeric>
#include <string>
#include <sstream>
#include <complex>
#include <vector>
#include <array>
#include <list>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>
using namespace std;
typedef long long unsigned int ll;

#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))

int GCD(int a, int b){
   return b ? GCD(b, a%b) : a;
}

int LCM(int a, int b){
   return (a * b)/(GCD(a, b));
}

int main(){
   char b;
   cin >> b;
   if(b == 'A'){
      cout << 'T' << endl;
   }
   if(b == 'T'){
      cout << 'A' << endl;
   }
   if(b == 'G'){
      cout << 'C' << endl;
   }
   if(b == 'C'){
      cout << 'G' << endl;
   }
   return 0;
}