t=int(input())
s=[input().split() for i in range(t)]

for i in range(t):
    v=int(s[i][0])
    if v<=2:
        print('X')
    elif v==3:
        if  '-oo'==s[i][1] or 'o-o'==s[i][1] or 'oo-'==s[i][1] or 'ooo'==s[i][1]:
            print('O')
        else:
            print('X')
    else:
        flag=True
        for j in range(v-2):
            if '-oo'==s[i][1][j:j+3] or 'oo-'==s[i][1][j:j+3] or 'ooo'==s[i][1][j:j+3]:
                print('O')
                flag=False
                break

        if flag:
            for j in range(v-3):
                if '-o--'==s[i][1][j:j+4] or '--o-'==s[i][1][j:j+4]:
                    print('O')
                    flag=False
                    break
            
            if flag:
                flag1 = True
                count = 0
                for j in range(v):
                    if (s[i][1][j] == 'o' and flag1) or (s[i][1][j] == 'o' and not flag1 and count % 2 == 0):
                        flag1 = False
                        count = 0
                    elif s[i][1][j] == 'x':
                        flag1 = True
                        count = 0
                    elif s[i][1][j] == '-':
                        count += 1
                    elif s[i][1][j] == 'o' and not flag1 and count % 2 == 1:
                        print('O')
                        flag = False
                        break
                
                if flag:
                    print('X')