s=["-oo","oo-","-o--","--o-","ooo"]
for _ in range(int(input())):
    a,b=input().split();ans="X"
    c=0;d=0;f=0
    while d<len(b):
    	if b[d]=="-" and f:
    		c+=1
    	elif b[d]=="o":
    		if c&1 and f:
    			ans="O"
    		f=1
    	if b[d]=="x":
    		f=0
    	if b[d]!="-":
    		c=0
    	d+=1
    for i in range(len(b)):
        for j in s:
            if b[i:i+len(j)]==j:
                ans="O"
    print(ans)