def has_three_consecutive_o(s):
    n = len(s)
    for i in range(n - 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)
    if has_three_consecutive_o(S):
        print("O")
        continue
    win = False
    for i in range(N):
        if S[i] == '-':
            # Check left two
            if i >= 2 and S[i-2] == 'o' and S[i-1] == 'o':
                win = True
                break
            # Check middle
            if i >= 1 and i < N-1 and S[i-1] == 'o' and S[i+1] == 'o':
                win = True
                break
            # Check right two
            if i <= N-3 and S[i+1] == 'o' and S[i+2] == 'o':
                win = True
                break
    print("O" if win else "X")