def has_three_consecutive_o(s):
    n = len(s)
    for i in range(n - 2):
        if s[i] == 'o' and s[i+1] == 'o' and s[i+2] == 'o':
            return True
    return False

def can_o_win_next_move(s):
    n = len(s)
    for i in range(n):
        if s[i] != '-':
            continue
        # Check left two
        if i - 2 >= 0 and s[i-1] == 'o' and s[i-2] == 'o':
            return True
        # Check left and right
        if i - 1 >= 0 and i + 1 < n and s[i-1] == 'o' and s[i+1] == 'o':
            return True
        # Check right two
        if i + 2 < n and s[i+1] == 'o' and s[i+2] == 'o':
            return True
    return False

T = int(input())
for _ in range(T):
    N, S = input().split()
    S = list(S)
    if has_three_consecutive_o(S):
        print("O")
        continue
    if can_o_win_next_move(S):
        print("O")
    else:
        print("X")