import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Comparator;
import java.util.PriorityQueue;

public class Main {
    static int N = 10010, M = 110;
    static int n, m;
    static Person[] p = new Person[N];//存储所有的个人记录

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] s1 = br.readLine().split(" ");
        n = Integer.parseInt(s1[0]);
        m = Integer.parseInt(s1[1]);
        for (int i = 0; i < n; i++) {
            int h, m, s, service_time;
            String[] s2 = br.readLine().split(" ");
            service_time = Integer.parseInt(s2[1]);
            String[] s3 = s2[0].split(":");
            h = Integer.parseInt(s3[0]);
            m = Integer.parseInt(s3[1]);
            s = Integer.parseInt(s3[2]);
            service_time = Math.min(service_time, 60);//最多服务60分钟
            //转化为秒
            p[i] = new Person(h * 3600 + m * 60 + s, service_time * 60);

        }
        //按照到达时间升序排序
        Arrays.sort(p, 0, n, new Comparator<Person>() {
            @Override
            public int compare(Person o1, Person o2) {
                return o1.arrive_time - o2.arrive_time;
            }
        });
        //存储m个窗口的结束时刻(或者说是可用的时刻)
        PriorityQueue<Integer> q = new PriorityQueue();
        for (int i = 0; i < m; i++) {
            q.add(8 * 3600);//8点，转为秒数
        }
        int sum = 0;//总共等待时间
        int cnt = 0;//享受到服务的人数
        for (int i = 0; i < n; i++) {
            int w = q.poll();
            if (p[i].arrive_time > 17 * 3600) break;//该同志及后面的人木得服务
            //该同志开始享受服务的时间
            int start_time = Math.max(p[i].arrive_time, w);
            sum += start_time - p[i].arrive_time;
            cnt++;
            //更新该窗口的结束时刻
            q.add(start_time + p[i].service_time);
        }
        System.out.printf("%.1f\n", (double)sum / cnt / 60);//我们按秒计算的，转为分钟
    }
}
class Person {
    int arrive_time;//到达时间，秒
    int service_time;//服务时间，秒

    public Person(int arrive_time, int service_time) {
        this.arrive_time = arrive_time;
        this.service_time = service_time;
    }
}