use std::cmp::Reverse;


fn main() {
    let mut nk = String::new();
    std::io::stdin().read_line(&mut nk).ok();
    let nk: Vec<usize> = nk.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nk[0];
    let k = nk[1];
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<isize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let mut b = String::new();
    std::io::stdin().read_line(&mut b).ok();
    let b: Vec<isize> = b.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut orders = (0..n).collect::<Vec<_>>();
    orders.sort_by_key(|&i| Reverse(a[i] - b[i]));
    let mut result = vec!["B"; n];
    for &i in orders.iter().take(k) { result[i] = "A"; }
    println!("{}", result.join(""));
}