#!/usr/bin/env python3
import sys
input = sys.stdin.readline

t = int(input())
for _ in range(t):
    n, s = input().split()
    n = int(n)
    if "ooo" in s:
        print("O")
        continue
    if "oo-" in s:
        print("O")
        continue
    if "-oo" in s:
        print("O")
        continue
    if "o-o" in s:
        print("O")
        continue
    if "o---o" in s:
        print("O")
        continue
    seed = s.count("-o-")
    side = s.count("xo-") + s.count("-ox")
    if seed > 0 and side > 0:
        print("O")
        continue
    print("X")