题解 | 好串

import java.util.Scanner;

import java.util.Stack;

// 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);
        String s = in.nextLine();
        Stack<Character> stack = new Stack<>();
        for(Character c : s.toCharArray()){
            if( !stack.isEmpty() && stack.peek() == 'a' && c == 'b'){
                stack.pop();
            }else{
                stack.push(c);
            }
        }
        System.out.println(stack.isEmpty() ? "Good" : "Bad");
        

    }
}