#include<bits/stdc++.h>
using namespace std;


int main(){
    int n; cin >> n;
    int one = 0;
    int two = 0;
    for (int i = 0; i<n ; i++){
        int c; cin >> c;
        if (c == 0) continue;
        else if (c == 1) one += 1;
        else if (c == 2) two += 1;
        else {
            cout << "B" << endl;
            return 0;
        }
    }
    if (one % 2 == 1 and two == 0) cout << "A" << endl;
    else if (one % 2 == 1 and two == 1) cout << "A" << endl;
    else cout << "B" << endl;
    return 0;
}