use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let t: usize = itr.next().unwrap().parse().unwrap();
    let mut out = Vec::new();
    for _ in 0..t {
        let n: usize = itr.next().unwrap().parse().unwrap();
        let s: Vec<char> = itr.next().unwrap().chars().collect();

        let mut oo = 0;
        let mut idx = 0;
        while idx < n {
            if s[idx] == 'o' {
                let mut tmp = 0;
                idx += 1;
                while idx < n && s[idx] == '-' {
                    tmp += 1;
                    idx += 1;
                }
                if idx < n && s[idx] == 'o' {
                    oo = std::cmp::max(oo, tmp);
                }
            }
            idx += 1;
        }
        if oo % 2 != 0 {
            writeln!(out, "O").ok();
            continue;
        }

        let mut o = false;
        if n > 2 {
            for i in 0..n - 2 {
                if s[i] == 'o' && s[i + 1] == 'o' && s[i + 2] != 'x' {
                    o = true;
                }
                if s[i] != 'x' && s[i + 1] == 'o' && s[i + 2] == 'o' {
                    o = true;
                }
                if s[i] == 'o' && s[i + 1] != 'x' && s[i + 2] == 'o' {
                    o = true;
                }
                if i < n - 3 {
                    if s[i] == '-' && s[i + 1] == 'o' && s[i + 2] == '-' && s[i + 3] == '-' {
                        o = true;
                    }
                    if s[i] == '-' && s[i + 1] == '-' && s[i + 2] == 'o' && s[i + 3] == '-' {
                        o = true;
                    }
                }
            }
        }

        if o {
            writeln!(out, "O").ok();
        } else {
            writeln!(out, "X").ok();
        }
    }
    stdout().write_all(&out).unwrap();
}