win3 = set([
    "ooo",
    "oo-",
    "o-o",
    "-oo",
])
win4 = set([
    "--o-",
    "-o--",
])
win5 = set([
    "o---o",
])


def RunLengthEncoding(S):
    res = []
    N = len(S)
    i = 0
    while i < N:
        cnt = 1
        while i < N - 1 and S[i] == S[i + 1]:
            cnt += 1
            i += 1
        res.append((S[i], cnt))
        i += 1
    return res


def game(N, S):
    for i in range(N - 2):
        sss = S[i: i + 3]
        if sss in win3:
            return True

    for i in range(N - 3):
        ssss = S[i:i+4]
        if ssss in win4:
            return True

    RLE = RunLengthEncoding(S)
    M = len(RLE)
    for i in range(M - 2):
        k, v = RLE[i]
        if k == "o":
            kc, vc = RLE[i+1]
            if kc == "-" and vc % 2 == 1 and RLE[i+2][0] == "o":
                return True
    return False


if __name__ == "__main__":
    T = int(input())
    ans = []
    for _ in range(T):
        _, S = input().split()
        N = len(S)
        if game(N, S):
            ans.append("O")
        else:
            ans.append("X")
    print(*ans, sep="\n")