public class Solution {
    public static String solution(String play_time, String adv_time, String[] logs) {
        int ad[] = new int[360000];
        int N = strToSec(play_time); // 전체 구간을 초 단위로 환산.
        int len = strToSec(adv_time); // 광고 구간을 초 단위로 환산.
        for (String log : logs) { // 해당 구간에 시청자 수를 카운트
            String sp[] = log.split("-");
            int start = strToSec(sp[0]);
            int end = strToSec(sp[1]);
            for (int i = start; i < end; i++)
                ad[i] += 1;
        }
        long sum = 0, maxSum = 0;
        int idx = 0, lo = 0;
        for (int i = 0; i < len; i++)
            sum += ad[i];
        maxSum = sum;
        // 투 포인터 방식 : 가장 많은 시청자수 구간을 찾아서 그때의 시작시간을 저장
        for (int hi = len; hi < N; hi++) {
            sum += ad[hi];
            sum -= ad[lo++];
            if(sum > maxSum){
                maxSum = sum;
                idx = hi - len + 1;
            }
        }
        String answer = secToStr(idx);
        return answer;
    }
    private static String secToStr(int t) {
        return String.format("%02d:%02d:%02d", t/3600, (t/60) % 60, t%60);
    }
    private static int strToSec(String time) {
        String sp[] = time.split(":");
        int ret = Integer.parseInt(sp[0]) * 3600;
        ret += Integer.parseInt(sp[1]) * 60;
        ret += Integer.parseInt(sp[2]);
        return ret;
    }
    public static void main(String[] args) {
        String play_time1 = "02:03:55";
        String play_time2 = "99:59:59";
        String play_time3 = "50:00:00";
        String adv_time1 = "00:14:15";
        String adv_time2 = "25:00:00";
        String adv_time3 = "50:00:00";
        String log1[] = {"01:20:15-01:45:14", "00:40:31-01:00:00", "00:25:50-00:48:29", "01:30:59-01:53:29", "01:37:44-02:02:30"};
        String log2[] = {"69:59:59-89:59:59", "01:00:00-21:00:00", "79:59:59-99:59:59", "11:00:00-31:00:00"};
        String log3[] = {"15:36:51-38:21:49", "10:14:18-15:36:51", "38:21:49-42:51:45"};
        System.out.println(solution(play_time1, adv_time1, log1));
        System.out.println(solution(play_time2, adv_time2, log2));
        System.out.println(solution(play_time3, adv_time3, log3));
    }
}