def main():
    import sys
    input = sys.stdin.read().split()
    T = int(input[0])
    idx = 1
    for _ in range(T):
        N = int(input[idx])
        S = input[idx+1]
        idx += 2
        
        # Check if there are already three consecutive 'o's
        has_three = False
        for i in range(len(S)-2):
            if S[i] == 'o' and S[i+1] == 'o' and S[i+2] == 'o':
                has_three = True
                break
        if has_three:
            print('O')
            continue
        
        # Check if O can win in the next move
        can_win = False
        for i in range(len(S)):
            if S[i] != '-':
                continue
            # Check left two
            if i >= 2 and S[i-1] == 'o' and S[i-2] == 'o':
                can_win = True
                break
            # Check left and right
            if i >= 1 and i < len(S)-1 and S[i-1] == 'o' and S[i+1] == 'o':
                can_win = True
                break
            # Check right two
            if i < len(S)-2 and S[i+1] == 'o' and S[i+2] == 'o':
                can_win = True
                break
        if can_win:
            print('O')
        else:
            print('X')

if __name__ == '__main__':
    main()