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

t = int(input())
for _ in range(t):
    n, s = input().split()
    s = "x" + s + "x"
    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
    if "--o-" in s:
        print("O")
        continue
    if "-o--" in s:
        print("O")
        continue
    print("X")