import sys

sys.setrecursionlimit(10 ** 6)
from bisect import *
from collections import *
from heapq import *

def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def SI(): return sys.stdin.readline()[:-1]
def LLI(rows_number): return [LI() for _ in range(rows_number)]
int1 = lambda x: int(x) - 1
def MI1(): return map(int1, sys.stdin.readline().split())
def LI1(): return list(map(int1, sys.stdin.readline().split()))
p2D = lambda x: print(*x, sep="\n")
dij = [(1, 0), (0, 1), (-1, 0), (0, -1)]

def main():
    def win():
        pi=-1
        for i in range(n):
            if s[i]=="o":
                if pi==-1:pi=i
                else:
                    if (i-pi)%2:pi=i
                    else:return True
            elif s[i]=="x":pi=-1
            s3=s[i:i+3]
            if i+3<=n and s3=="ooo":return True
            if i+3<=n and s3=="-oo":return True
            if i+3<=n and s3=="o-o":return True
            if i+3<=n and s3=="oo-":return True
            if i+4<=n and s[i:i+4]=="-o--":return True
            if i+4<=n and s[i:i+4]=="--o-":return True
            if i+5<=n and s[i:i+5]=="o---o":return True
        return False

    for _ in range(II()):
        n,s=SI().split()
        n=int(n)
        if win():print("O")
        else:print("X")

main()