#!usr/bin/env python3
from collections import defaultdict, deque
from heapq import heappush, heappop
from itertools import permutations, accumulate
import sys
import math
import bisect
def LI(): return [int(x) for x in sys.stdin.buffer.readline().split()]
def I(): return int(sys.stdin.buffer.readline())
def LS():return [list(x) for x in sys.stdin.readline().split()]
def S():
    res = list(sys.stdin.readline())
    if res[-1] == "\n":
        return res[:-1]
    return res
def IR(n):
    return [I() for i in range(n)]
def LIR(n):
    return [LI() for i in range(n)]
def SR(n):
    return [S() for i in range(n)]
def LSR(n):
    return [LS() for i in range(n)]

sys.setrecursionlimit(1000000)
mod = 1000000007

def solve():
    t = I()
    f = {"o":0, "x":1, "-":2}
    for _ in range(t):
        n,s = input().split()
        n = int(n)
        if n < 5:
            print("X")
            continue
        c = [0,0,0]
        c[f[s[0]]] += 1
        c[f[s[1]]] += 1
        for i in range(2,n):
            c[f[s[i]]] += 1
            if c == [2,0,1] or c == [3,0,0]:
                print("O")
                break
            c[f[s[i-2]]] -= 1
        else:
            c = [0,0,0]
            c[f[s[0]]] += 1
            c[f[s[1]]] += 1
            c[f[s[2]]] += 1
            for i in range(3,n):
                c[f[s[i]]] += 1
                if c == [1,0,3] and s[i] == "-" and s[i-3] == "-":
                    print("O")
                    break
                c[f[s[i-3]]] -= 1
            else:
                print("X")
    return

#Solve
if __name__ == "__main__":
    solve()