use std::io;

fn main() {
    let mut input = String::new();
    io::stdin()
        .read_line(&mut input)
        .expect("Failed to read line");
    let mut n: u64 = input.trim().parse().expect("Not a number");

    let mut result = Vec::new();

    while n > 1 {
        if (n - 1) % 2 == 0 {
            result.push('A');
            n = (n - 1) / 2;
        } else {
            result.push('B');
            n = (n - 2) / 2;
        }
    }

    result.reverse();
    let result: String = result.iter().collect();
    println!("{}", result);
}