题解 | #DNA序列#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        // while (in.hasNextInt()) { // 注意 while 处理多个 case
        //     int a = in.nextInt();
        //     int b = in.nextInt();
        //     System.out.println(a + b);
        // }
        String goalStr = "";
        String line = in.nextLine();
        int N = in.nextInt();
        int len = line.length();

        int cgCount = 0;
        for (int i = 0; i <= len - N; i++) {
            String sub = line.substring(i, i + N);
            int temp = 0;
            for (int j = 0; j < N; j++) {
                if (sub.charAt(j) == 'C' || sub.charAt(j) == 'G') {
                    temp++;
                }
            }
            if (temp > cgCount) {
                goalStr = sub;
                cgCount = temp;
            }
        }
        System.out.print(goalStr);
    }
}