import std.algorithm, std.conv, std.range, std.stdio, std.string;

void main()
{
  auto n = readln.chomp.to!size_t;
  auto c = readln.split.to!(int[]).filter!"a > 0".array;
  n = c.length;

  auto b = c.count!"a >= 2";
  if (b == 0) {
    writeln(n % 2 == 0 ? "B" : "A");
    return;
  }

  if (b == 1 && c.count!"a == 2" == 1) {
    writeln(n % 2 == 0 ? "A" : "B");
    return;
  }

  writeln("B");
}