import re
import math

t = int(input())
for _ in range(t):
    n, line = input().split()
    if line.find('ooo') != -1 \
    or line.find('-oo') != -1 \
    or line.find('oo-') != -1 \
    or line.find('--o-') != -1 \
    or line.find('-o--') != -1:
        print('O')
    else:
        limit = int(n) // 2
        for i in range(1, limit):
            desire = 'o' + '-'*(2*i-1) + 'o'
            if line.find(desire) != -1:
                print('O')
                break
        else:
            print('X')