我怎么样例二过了

#include<bits/stdc++.h>
#define ll long long
#pragma GCC optimize(2)
#define un unsigned
#define int long long
#define db double
#define inf 1000000000000000
#define st string
#define ct const
#define xh(a,b,c) for(int a=b;a<=c;a++)
#define wx while(1)
#define dn(a,b,c) for(int a=b;a>=c;a--)
using namespace std;
string s;
void dfs(string s){
	bool f1=0,f2=0;
	xh(i,0,s.size()-1){
		if(s[i]!='0')f1=1;
		if(s[i]!='1')f2=1;
	}
	if(!f1){
		cout<<'A';
		return ;
	}
	if(!f2){
		cout<<'B';
		return ;
	}
	cout<<'C';
	string s1,s2;
	xh(i,0,s.size()/2-1)s1+=s[i];
	dfs(s1);
	xh(i,s.size()/2,s.size()-1)s2+=s[i];
	dfs(s2);
}
signed main(){
	cin>>s;
	dfs(s);
	return 0;
}