T = int(input())
win = ["ooo", "oo-", "o-o", "-oo", "--o-", "-o--"]

for i in range(1,500):
    temp = "o"+"-"*(2*i+1)+"o"
    win.append(temp)

for _ in range(T):
    flag = 0
    N, S = input().split()
    for x in win:
        if x in S:
            flag = 1
            break
    if flag:
        print("O")
    else:
        print("X")