题解 | #DNA序列#

import java.io.*;
import java.util.*;

public class Main{
    public static void main(String [] args) throws Exception{
        BufferedReader bf =  new BufferedReader(new InputStreamReader(System.in));
        char [] arr = bf.readLine().toCharArray();
        int num =  Integer.parseInt(bf.readLine());
        int max = 0;
        int start = 0;
        for(int i = 0; i<arr.length-num; i++){
            int count=0;
            for(int j=i; j < num + i; j++){
                if(arr[j] == 'C' || arr[j] == 'G'){
                    count++;
                }
            } 
            if(max < count){
                start = i;
                max= count;
            }
        }
        StringBuilder builder = new StringBuilder();
        for(int i = start; i < start + num; i++) {
              builder.append(arr[i]);
        }
            System.out.println(builder.toString());
    }
}