# coding: utf-8
T=int(input())

for i in range(T):
    N,S=input().split()
    N=int(N)
    S=list(S)
    
    flg=False
    L=[0 for i in range(N)]
    R=[0 for i in range(N)]
    cnt_brank=0
    
    for i in range(N):
        if S[i]=="-":
            cnt_brank+=1
        elif S[i]=="o":
            L[i]=cnt_brank
            cnt_brank=0
            if i>=cnt_brank+1:
                if S[i-cnt_brank-1]=="o" and cnt_brank%2==1:
                    flg=True
                    
        else:
            cnt_brank=0
        
        if i>0:
            if S[i-1]==S[i]=="o":
                if i>1:
                    if S[i-2]=="-" or S[i-2]=="o":
                        flg=True
                if i<N-1:
                    if S[i+1]=="-" or S[i+1]=="o":
                        flg=True
    
    
    for i in range(1,N+1):
        if S[-i]=="-":
            cnt_brank+=1
        elif S[-i]=="o":
            R[-i]=cnt_brank
            cnt_brank=0
        else:
            cnt_brank=0
    
    for i in range(N):
        if L[i]>=2 and R[i]>=2:
            flg=True
            
    if flg:
        print("O")
    else:
        print("X")