def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))
mod=10**9+7

def main():
    T=I()
    for _ in range(T):
        a,S=input().split()
        S=["x"]+list(S)+["x"]
        N=len(S)
        now="x"
        length=1
        f=0
        for i in range(1,N-1):
            if S[i]==now:
                length+=1
            else:
                now=S[i]
                length=1
                
            if now=="o" and length==3:
                f=1
                break
            elif now=="o" and length==2 and (S[i-1]=="-" or S[i+1]=="-"):
                f=1
                break
            elif now=="-" and length%2==1 and (S[i-1]=="o" and S[i+1]=="o"):
                f=1
                break
            
        if f==1:
            print("O")
        else:
            print("X")
        
        
    
    


main()