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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>

#define _CRT_SECURE_NO_WARNINGS
#define TLong long long 

// fact(n)
int fact(int n){
	if(n == 1)	return 1;
	else return (n * fact(n - 1));
}

// combination(n,r)
int combination(int n, int r){
	if(r == 0 || r == n)	return 1;
	else if(r == 1)	return n;
	return (combination(n - 1, r - 1) + combination(n - 1, r));
}

// gcd(a,b)
int gcd(int a,int b){
	return (b == 0) ? a : gcd(b, a % b);
}

// lcm(a.b)
int lcm(int a,int b){
	return (a * b) / gcd(a,b);
}

// qsort(array, size, sizeof(int),comp);
int comp(const int *a,const int *b){
	return (*a - *b);
}

// append(array,*size,addNum)
void append(int *array,int *size,int num){
	realloc(array, sizeof(int) * (*size + 1));
	array[(*size)] = num;
	++(*size);
}

// pop(array,*size) & nongetpop(array,*size)
int pop(int *array,int *size){
	int temp = array[(*size - 1)];
	realloc(array,sizeof(int) * (*size - 1));
	--(*size);
	return temp;
}

void nongetpop(int *array,int *size){
	realloc(array,sizeof(int) * (*size - 1));
	--(*size);
}

int main(int argc, char const *argv[])
{
	char ch;
	scanf("%c",&ch);
	if(ch == 'A')	puts("T");
	else if(ch == 'G')	puts("C");
	else if(ch == 'T')	puts("A");
	else	puts("G");
	return 0;
}