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<bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define REP(i, n) for(int i = 1; i < (int)(n); i++)
typedef long long ll;
#define NP next_permutation
#define MP make_pair

int dp[100];

//最大公約数
int gcd(int x, int y){
  if(x % y == 0) return y;
  return gcd(y, x % y);
}
//最小公倍数
int lcm(int x, int y){
  return x * y / gcd(x, y);
}
//フィボナッチ数列
//配列dpを-1で初期化する
int fib(int n){
  if(n == 0 || n == 1) return dp[n] = 1;
  if(dp[n] != -1) return dp[n];
  return dp[n] = fib(n - 1) + fib(n - 2);
}
//階乗計算(factorial)
int fact(int n){
  if(n = 1) return 1;
  return n * fact(n - 1);
}
//累乗計算(Exponentiation)
//x**y
ll expo(int x, int y){
  ll ans = 1;
  rep(i, y){
    ans *= x;
  }
  return ans;
}
//桁数
int keta(ll x){
  if(x == 0) return 1;
  int res = 0;
  while(x){
    x /= 10;
    res++;
  }
  return res;
}


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