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 9.2.1) (judge verdict: Wrong Answer)

/* ex5_4
  kt125*/

#include<stdio.h>
#include<string.h>

int main(void){
    int count = 0, ans=0;
    char str[11], *ptr;
    scanf("%s", &str[0]);

    //'A','G','C','T'の全てを'#'に置き換える。
    for(int i= 0; i< strlen(str);i++){
        if(str[i] == 'A' || str[i] == 'C' ||
           str[i] == 'G' || str[i] == 'T'){
               str[i] = '#';
        }
    }
    ptr = str; //strの先頭アドレスをptrに渡す
    //連続する'#'の最大数ansを求める
    while(*ptr){
        if( *ptr == '#'){ 
            count++;
            if(ans < count) ans = count;
        }else{ //'#'以外の文字が出たらcountをリセット
            count = 0;
        }
        ptr++;
    }

    printf("%d\n", ans);
    return 0;
}