t = int(input())
for _ in range(t):
    info = list(input().split())
    n, s = info

    n = int(n)
    li = s.split("x")
    for string in li:
        if len(string) <= 2:
            continue
        if string == "-o-":
            continue
        if string[1:-1].count("o") > 0:
            print("O")
            break
        if string[0] == "o" and string[-1] == "o" and len(string)  % 2 == 1:
            print("O")
            break
    else:
        print("X")