T = int(input())
N, S = [], []
for i in range(T):
    a, b = input().split()
    N.append(int(a))
    S.append(b)

def ans_check2(S):
    tmp = -1
    for i in range(len(S)):
        if tmp <= 0 and S[i] == 'o':
            tmp = 0
        
        if tmp >= 0 and S[i] == '-':
            tmp += 1
        
        if tmp > 0 and S[i] == 'o':
            return True
                
        if S[i] == 'x':
            tmp = -1
    return False

def ans_check(S):
    lists = ['-oo', 'o-o', 'oo-', 'ooo']
    for i in range(len(S) - 2):
        if S[i: i+3] in lists:
            return True
    return ans_check2(S)


for i in range(len(S)):
    print('O' if ans_check(S[i]) else 'X')