def scan; gets.chomp!.split.map(&:to_i); end

def flip(turn)
    turn == :a_san ? :b_san : :a_san
end

@memo={}
def dfs(c, turn = :a_san)
    c.delete(0)
    
    return flip(turn) if c.empty?
    
    return @memo[[c,turn]] if @memo[[c,turn]]
    
    c.each_index{|i|
        c[i] -= 1
        return @memo[[c,turn]]=turn if dfs(c.clone, flip(turn)) == turn
        if turn == :b_san && 0 < c[i]
            c[i] -= 1
            return @memo[[c,turn]]=turn if dfs(c.clone, flip(turn)) == turn
            c[i] += 1
        end
        c[i] += 1
    }
    return @memo[[c,turn]]=flip(turn)
end

gets
c = scan

# End Of Line
abort if gets

puts dfs(c) == :a_san ? 'A' : 'B'