const MOD: u64 = 1_000000000 + 7;

fn main() {
    let mut sc = Scanner::new();
    let n = sc.next_usize();
    let mut d = sc.next_usize();

    let mut res = String::new();
    for i in 0..n {
        let c = n - i;
        if d > 0 && 1 + (c - 1) * 2 >= d {
            d -= 1;
            res.push('A')
        } else if d > 1 && c * 2 >= d {
            d -= 2;
            res.push('B')
        } else {
            res.push('C')
        }
    }
    println!("{}", res);
}


struct Scanner {
    reader: std::io::Stdin,
    tokens: std::collections::VecDeque<String>,
}

impl Scanner {
    fn new() -> Self {
        Scanner {
            reader: std::io::stdin(),
            tokens: std::collections::VecDeque::new(),
        }
    }

    fn next(&mut self) -> String {
        if self.tokens.is_empty() {
        let mut s = String::new();
            loop {
                self.reader.read_line(&mut s).ok();
                let s = s.trim();
                if s.len() != 0 {
                    for it in s.split_whitespace() {
                        self.tokens.push_back(it.into())
                    }
                    break;
                }
            }
        }
        self.tokens.pop_front().unwrap()
    }

    fn next_generics<T>(&mut self) -> T where
        T: std::str::FromStr + std::marker::Copy,
        <T as std::str::FromStr>::Err: std::fmt::Debug
    {
        self.next().parse().unwrap()
    }
    
    #[allow(dead_code)] fn next_i32(&mut self) -> i32 { self.next_generics::<i32>() }
    #[allow(dead_code)] fn next_i64(&mut self) -> i64 { self.next_generics::<i64>() }
    #[allow(dead_code)] fn next_u64(&mut self) -> u64 { self.next_generics::<u64>() }
    #[allow(dead_code)] fn next_usize(&mut self) -> usize { self.next_generics::<usize>() }
}