win = ["ooo", "-oo", "o-o", "oo-", "-o--", "--o-"]
def solve():
    n, S = input().split()
    for w in win:
        if w in S:
            print("O")
            return
    S = S.split("o")
    for s in S:
        if "x" not in s and len(s) % 2 == 1 and len(s) >= 3:
            print("O")
            return
    print("X")
    
for _ in range(int(input())):
    solve()