#include<bits/stdc++.h>
using namespace std;
string a;
int i,j,s,s1,s2,c,m,n;
void cut(string d)
{
	int s1=0;
	int s=d.size();
	for(int i=0;i<s;i++) if(d[i]=='0') s1++;
	if(s1==s) 
	{
		cout<<"A";
		return;
	}
	else if(s1==0) 
	{
		cout<<"B";
		return;
	}
	else 
	{
		cout<<"C";
	    cut(d.substr(0,s/2));
	    cut(d.substr(s/2));
	}
}
int main()
{
	getline(cin,a);
	cut(a);
	return 0;
}

wa了第九点……

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