MOD = 10 ** 9 + 7
INF = 10 ** 10
import sys
sys.setrecursionlimit(100000000)
dy = (-1,0,1,0)
dx = (0,1,0,-1)

def main():
    t = int(input())
    for _ in range(t):
        l = input().split()
        n = int(l[0])
        s = l[1]

        if s.count('ooo') or s.count('oo-') or s.count('-oo') or s.count('--o-') or s.count('-o--'):
            print('O')
            continue
       
        cnt = -INF
        ans = 'X'
        for i in range(n):
            if s[i] == 'o':
                if cnt < 0:
                    cnt = 0
                elif cnt%2 == 1:
                    ans = 'O'
                    break
                else:
                    cnt = 0
            elif s[i] == '-':
                cnt += 1
            else:
                cnt = -INF
        
        print(ans)

if __name__ =='__main__':
    main()