#include <iostream>
using namespace std;
int main(int argc, char* argv[])
{
	int N;
	cin>>N;
	int i;
	int c;
	int n0=0,n1=0,n2=0,n3=0;
	for (i=0;i<N;i++){
		cin>>c;
		if (c==0){
			n0++;
		}else if (c==1){
			n1++;
		}else if (c==2){
			n2++;
		}else{
			n3++;
		}
	}
	N-=n0;
	if (n3>0 || n2>1){
		cout<<"B"<<endl;
		return 0;
	}
	if (n2==0){
		if (N%2==1){
			cout<<"A"<<endl;
		}else{
			cout<<"B"<<endl;
		}
		return 0;
	}
	if (n2==1){
		if (N%2==1){
			cout<<"B"<<endl;
		}else{
			cout<<"A"<<endl;
		}
		return 0;
	}
	cout<<"B"<<endl;
	return 0;
}