s=["o-o","-oo","oo-","-o--","--o-","o-o-o","ooo"]
for _ in range(int(input())):
    a,b=input().split();ans="X"
    for i in range(len(b)):
        for j in s:
            if b[i:i+len(j)]==j:
                ans="O"
    print(ans)