#![allow(non_snake_case)]

use std::io::{ self, prelude::* };

macro_rules! pick {
    ($tokens:expr) => {
        $tokens.next().unwrap().parse().expect("parse error")
    }
}

fn main() {
    let mut s = String::new();
    io::stdin().read_to_string(&mut s).expect("i/o error");
    let mut tokens = s.split_whitespace();

    let N: usize = pick!(tokens);
    let D: usize = pick!(tokens);

    let s = if D < N {
        let na = D;
        let nc = N - D;
        "A".repeat(na) + &"C".repeat(nc)
    }
    else {
        let nb = D - N;
        let na = N - nb;
        "A".repeat(na) + &"B".repeat(nb)
    };

    println!("{}", s);
}