use std::io::Write;
use std::collections::*;

type Map<K, V> = BTreeMap<K, V>;
type Set<T> = BTreeSet<T>;
type Deque<T> = VecDeque<T>;

fn run() {
    input! {
        t: usize,
        ask: [(usize, bytes); t],
    }
    let out = std::io::stdout();
    let mut out = std::io::BufWriter::new(out.lock());
    for (n, mut s) in ask {
        for s in s.iter_mut() {
            *s -= b'A';
        }
        let s = s;
        let mut z = vec![0, n];
        for i in 1..n {
            if s[i] != s[i - 1] {
                z.push(i);
            }
            if z.len() >= 6 {
                break;
            }
        }
        for i in 0..z.len() {
            let x = z[i];
            if x + 1 < n {
                z.push(x + 1);
            }
            if x + 2 < n {
                z.push(x + 2);
            }
            if x >= 1 {
                z.push(x - 1);
            }
            if x >= 2 {
                z.push(x - 2);
            }
        }
        z.sort();
        z.dedup();
        let mut ans = bob(s.clone());
        for (j, &r) in z.iter().enumerate() {
            for &l in z.iter().take(j) {
                let mut s = s.clone();
                s[l..r].iter_mut().for_each(|s| *s ^= 1);
                ans = bob(s).min(ans);
            }
        }
        let ans = ans.into_iter().map(|a| (a + b'A') as char).collect::<String>();
        writeln!(out, "{}", ans).ok();
    }
}

fn main() {
    run();
}

fn bob(mut a: Vec<u8>) -> Vec<u8> {
    if let Some(l) = a.iter().position(|a| *a == 0) {
        let r = (l..a.len()).find(|&k| a[k] == 1).unwrap_or(a.len());
        a[l..r].fill(1);
    }
    a
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------