# coding:UTF-8
import sys

MOD = 10 ** 9 + 7
INF = float('inf')

T = int(input())    # 数字

res = []
for _ in range(T):
    N, S = input().split()     # スペース区切り連続文字列
    N = int(N)

    # "ooo"
    # "-oo"
    # "oo-"
    f = 0
    for i in range(N-3):
        s = S[i:i+3]
        if s == "ooo" or s == "-oo" or s == "oo-":
            f = 1

    # "-o--"
    # "--o-"
    for i in range(N-4):
        s = S[i:i+4]
        if s == "-o--" or s == "--o-":
            f = 1

    # "o---o"
    m = 0
    h = 0
    for i in range(N-4):
        if S[i] == "-":
            if m == 1:
                h += 1
        elif S[i] == "o":
            if m == 1:
                if h % 2 == 1:
                    f = 1
                else:
                    h = 0
            m = 1

    if f:
        res.append("O")
    else:
        res.append("X")

for r in res:
    print(r)