"""
출처:프로그래머스
https://school.programmers.co.kr/learn/courses/30/lessons/17676
"""

# 풀이 과정
# 누적합
from collections import defaultdict

Data = [0] * 24 * 60 * 60 * 1000


# for s in range(24*60*60):
#     Data[s]=0

def time_to_sec(x, y):
    global Data

    t = x.split(":")
    hour, minu, sec = int(t[0]), int(t[1]), float(t[2])
    end_time = (int(hour) * 60 * 60 + int(minu) * 60 + sec) * 1000

    blank = list(y)
    blank.pop()
    y = "".join(blank)

    # 시작 시간, 끝 시간
    start = end_time - float(y) * 1000 + 1
    start = max(0, start)
    end_time = min(24 * 60 * 60 * 1000 - 1, end_time + 999)
    start, end = int(start), int(end_time)

    for tra in range(start, end + 1):
        Data[tra] += 1

    return 0


def solution(lines):
    global Data

    for l in lines:
        d = l.split(" ")
        time = time_to_sec(d[1], d[2])

    result = 0
    count = 0
    result = max(Data)

    return result