pub mod io {
    pub fn scan<R: std::io::BufRead>(r: &mut R) -> Vec<u8> {
        let mut res = Vec::new();
        loop {
            let buf = match r.fill_buf() {
                Ok(buf) => buf,
                Err(e) if e.kind() == std::io::ErrorKind::Interrupted => continue,
                Err(e) => panic!("{}", e), 
            };
            let (done, used, buf) = match buf.iter().position(u8::is_ascii_whitespace) {
                Some(i) => (i > 0 || res.len() > 0, i + 1, &buf[..i]),
                None => (buf.is_empty(), buf.len(), buf),
            };
            res.extend_from_slice(buf);
            r.consume(used);
            if done { return res; }
        }
    }

    #[macro_export]
    macro_rules! scan {
        ($r:expr, [$t:tt; $n:expr]) => ((0..$n).map(|_| scan!($r, $t)).collect::<Vec<_>>());
        ($r:expr, [$t:tt]) => (scan!($r, [$t; scan!($r, usize)]));
        ($r:expr, ($($t:tt),*)) => (($(scan!($r, $t)),*));
        ($r:expr, Usize1) => (scan!($r, usize) - 1);
        ($r:expr, String) => (String::from_utf8(scan!($r, Bytes)).unwrap());
        ($r:expr, Bytes) => (io::scan($r));
        ($r:expr, $t:ty) => (scan!($r, String).parse::<$t>().unwrap());
    }

    #[macro_export]
    macro_rules! input {
        ($r:expr, $($($v:ident)* : $t:tt),* $(,)?) => {
            $(let $($v)* = scan!($r, $t);)*
        };
    }
}


fn run<R: std::io::BufRead, W: std::io::Write>(reader: &mut R, writer: &mut W) {
    input! {
        reader,
        n: usize, k: usize,
        a: [i64; n],
        b: [i64; n],
    }

    let mut v: Vec<_> = {
        a.iter()
            .zip(b.iter())
            .enumerate()
            .map(|(i, (a, b))| (a - b, i))
            .collect()
    };
    v.sort();

    let mut ans = vec![b'B'; n];
    for (_, i) in v.into_iter().rev().take(k) {
        ans[i] = b'A';
    }
    writer.write_all(&ans).ok();
    writer.write_all(b"\n").ok();
}

fn main() {
    let (stdin, stdout) = (std::io::stdin(), std::io::stdout());
    let ref mut reader = std::io::BufReader::new(stdin.lock());
    let ref mut writer = std::io::BufWriter::new(stdout.lock());
    run(reader, writer);
}