T = int(input())
for _ in range(T):
    N, S = input().split()
    N = int(N)
    
    if S.find("ooo") >= 0:
        print("O")
    elif S.find("o-o") >= 0:
        print("O")
    elif S.find("-o--") >= 0:
        print("O")
    elif S.find("--o-") >= 0:
        print("O")
    elif S.find("-oo") >= 0:
        print("O")
    elif S.find("oo-") >= 0:
        print("O")
    elif S.replace("--", "").find("o-o") >= 0:
        print("O")
    else:
        print("X")