fn solve() -> String {
    let mut temp = String::new();
    std::io::stdin().read_line(&mut temp).ok();
    let temp: Vec<&str> = temp.trim().split_whitespace().collect();
    let n = temp[0].parse::<usize>().unwrap();
    let s = temp[1];
    if s.contains("ooo") || s.contains("-oo") || s.contains("oo-") || s.contains("o-o-o") {
        return "O".to_string();
    }
    return "X".to_string();
}

fn main() {
    let mut t = String::new();
    std::io::stdin().read_line(&mut t).ok();
    let t: usize = t.trim().parse().unwrap();
    let mut result = Vec::with_capacity(t);
    for _ in 0..t {
        result.push(solve());
    }
    for v in result.iter() {
        println!("{}", v);
    }
}