def has_triplet(s):
    for i in range(len(s) - 2):
        if s[i] == 'o' and s[i+1] == 'o' and s[i+2] == 'o':
            return True
    return False

T = int(input())
for _ in range(T):
    N, S = input().split()
    N = int(N)
    count_o = S.count('o')
    count_x = S.count('x')
    rem = N - (count_o + count_x)
    if rem == 0:
        if has_triplet(S):
            print("O")
        else:
            print("X")
    else:
        found = False
        for i in range(N):
            if S[i] == '-':
                temp = S[:i] + 'o' + S[i+1:]
                if has_triplet(temp):
                    found = True
                    break
        if found:
            print("O")
        else:
            print("X")