T = int(input())
for _ in range(T):
    N, S = input().split()
    N = int(N)
    if 'ooo' in S:
        print('O')
        continue
    found = False
    for i in range(len(S)):
        if S[i] == '-':
            temp = S[:i] + 'o' + S[i+1:]
            if 'ooo' in temp:
                found = True
                break
    print('O' if found else 'X')