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


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

    for i in range(N - 4):
        sssss = S[i: i + 5]
        if sssss in win5:
            return True
    return False


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