fn main() {
    let mut xx = String::new();
    std::io::stdin().read_line(&mut xx).ok();
    let xx: Vec<i32> = xx.split_whitespace().flat_map(str::parse).collect();

    let diff = xx[1] - xx[0];

    let mut answer = vec!['A'; (xx[0] - diff.abs()) as usize];
    answer.extend(vec![
        match diff.cmp(&0) {
            std::cmp::Ordering::Greater => 'B',
            std::cmp::Ordering::Less => 'C',
            std::cmp::Ordering::Equal => 'A',
        };
        diff.unsigned_abs() as usize
    ]);

    let answer: String = answer.iter().collect();

    println!("{answer}");
}