for _ in range(int(input())):
    N,S = input().split()
    N = int(N)
    ret = "X"
    if "ooo" in S:
        ret = "O"
    if "oo-" in S:
        ret = "O"
    if "o-o" in S:
        ret = "O"
    if "-oo" in S:
        ret = "O"
    if "--o-" in S:
        ret = "O"
    if "_o__" in S:
        ret = "O"
    print(ret)