N = int(input())
for i in range(N):
    L,S = input().split()
    L = int(L)
    S = S + 'xxx'
    O = [0]*4

    j = 0
    while j<L:
        o=S[j:j+3].count('o')
        hai=S[j:j+3].count('-')
        if o + hai == 3:
            O[o]+=1
            j+=2
        j+=1
    if O[3]>0 or O[2]>0 or O[1]>=2:
        print('O')
    else:
        print('X')