from functools import total_ordering


@total_ordering
class OrderTime:
    def __init__(self, day: int, hour: int, minute: int) -> None:
        self.hour = hour
        self.minute = minute
        self.day = day

    @property
    def time_tuple(self) -> tuple[int, int, int]:
        return self.day, self.hour, self.minute

    def __eq__(self, __o: object) -> bool:
        if not isinstance(__o, OrderTime):
            raise ValueError
        return self.time_tuple == __o.time_tuple

    def __lt__(self, __o: object) -> bool:
        if not isinstance(__o, OrderTime):
            raise ValueError
        return self.time_tuple < __o.time_tuple

    def __str__(self) -> str:
        return f"{self.day} {self.hour}:{self.minute}"


class Order:
    def __init__(self, enter_day, enter_hour, enter_minute, out_day, out_hour, out_minute) -> None:
        self.enter_time = OrderTime(enter_day, enter_hour, enter_minute)
        self.out_time = OrderTime(out_day, out_hour, out_minute)

    def can_stay(self, _o: object) -> bool:
        if not isinstance(_o, Order):
            raise ValueError
        return self.out_time < _o.enter_time


def main():
    n, m = map(int, input().split())
    orders: list[Order] = []
    for _ in range(m):
        enter_day, enter_time, out_day, out_time = input().split()
        enter_day = int(enter_day)
        out_day = int(out_day)
        enter_hour, enter_minute = map(int, enter_time.split(":"))
        out_hour, out_minute = map(int, out_time.split(":"))
        orders.append(Order(enter_day, enter_hour, enter_minute,
                            out_day, out_hour, out_minute))

    orders.sort(key=lambda order: order.out_time)

    ctr = 0
    rooms = [Order(1, 23, 50, 1, 23, 59) for _ in range(n)]

    for order in orders:
        next_order = [-1, (-1, -1, -1)]
        for room_idx, room in enumerate(rooms):
            if room.can_stay(order) and next_order[1] < room.out_time.time_tuple:
                next_order = [room_idx, room.out_time.time_tuple]
        if next_order[0] == -1:
            continue
        rooms[next_order[0]] = order
        ctr += 1

    print(ctr)


if __name__ == "__main__":
    main()