#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1LL << 30;
int MOD = 1e9+7;
main(){
    int N;
    cin >> N;
    vector<int> A(N);
    for(int i = 0;i < N;i++)cin >> A[i];
    int ans = 0;
    for(int i = 0;i < N;i++)ans ^= A[i] == 1;
    if(ans)cout << "A" << endl;
    else cout << "B" << endl;
}