from typing import List


def checkio(game_result: List[str]) -> str:
    h = horizontal(game_result)
    v = vertical(game_result)
    d = diagonal(game_result)
    if h != "D":
        return h
    if v != "D":
        return v
    if d != "D":
        return d
    return "D"


def horizontal(game_result: List[str]) -> str:
    for row in game_result:
        cells = list(row)
        cells.sort()
        if cells[0] == '.':
            continue
        if cells[0] == cells[-1:][0]:
            return cells[0]
    return "D"


def vertical(game_result: List[str]) -> str:
    new_game_result = []
    for i in range(len(game_result)):
        new_game_result.append(game_result[0][i] + game_result[1][i] + game_result[2][i])
    return horizontal(new_game_result)


def diagonal(game_result: List[str]) -> str:
    if game_result[1][1] == '.':
        return "D"
    if game_result[0][0] == game_result[1][1] and game_result[1][1] == game_result[2][2]:
        return game_result[1][1]
    if game_result[0][2] == game_result[1][1] and game_result[1][1] == game_result[2][0]:
        return game_result[1][1]
    return "D"


if __name__ == '__main__':
    print("Example:")
    print(checkio(["X.O",
                   "XX.",
                   "XOO"]))

    # These "asserts" using only for self-checking and not necessary for auto-testing
    assert checkio([
        "X.O",
        "XX.",
        "XOO"]) == "X", "Xs wins"
    assert checkio([
        "OO.",
        "XOX",
        "XOX"]) == "O", "Os wins"
    assert checkio([
        "OOX",
        "XXO",
        "OXX"]) == "D", "Draw"
    assert checkio([
        "O.X",
        "XX.",
        "XOO"]) == "X", "Xs wins again"
    assert checkio([".O.", "XXX", ".O."]) == "X", "Xs wins again"
    assert checkio(["...", "XXX", "OO."]) == "X", "Xs wins again"
    print("Coding complete? Click 'Check' to review your tests and earn cool rewards!")