import java.io.*;
import java.util.*;


public class Main_yukicoder582 {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		int n = sc.nextInt();

		int[] c = new int[n];
		int xor = 0;
		for (int i = 0; i < n; i++) {
			c[i] = sc.nextInt();
			xor ^= c[i];
		}

		xor &= 0x3;

		if (xor == 0) {
			pr.println('B');
		} else if (xor == 1) {
			pr.println('A');
		} else if (xor == 2) {
			pr.println('B');
		} else {
			pr.println('A');
		}
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pr = new Printer(System.out);

		solve();

		pr.close();
		sc.close();
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}