题解 | 好串

import java.util.*;


// 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.next();
        Stack<Character> stack=new Stack();
        for(int i=0;i<s.length();i++){
            char c=s.charAt(i);
            if(!stack.isEmpty()&&stack.peek()=='a'&&c=='b'){
                stack.pop();
            }else {
                stack.push(c);
            }
        }
        System.out.println(stack.size()>0?"Bad":"Good");
    }
}