1017

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <vector>
#include <cstring>


using namespace std;

int counter[100];	//柜台
int gwclock = 8*3600;	//全局秒表
int total_wait = 0; //总等待
int N, K;

struct Person{

	int ahead_t;
	int wait_t;
	int serve_t;

	int serving_t;	//剩余未服务时间

	int arr_t;		//到达时间
};


vector<Person> bank_queue;	//队列
int queue_front;  //队首位置


bool greater_cmp(const Person &v1, const Person &v2){
	return v1.arr_t > v2.arr_t;
}





int main(){
	//初始化counter
	memset(counter, -1, sizeof(counter));


	scanf("%d %d", &N, &K);
	for (int i = 0; i < N; i++)
	{
		int HH, MM, SS, serve_t;
		scanf("%d:%d:%d %d", &HH, &MM, &SS, &serve_t);

		//初始化person
		struct Person person;
		person.wait_t = 0;
		person.serve_t = serve_t * 60;
		person.serving_t = serve_t * 60;
		person.arr_t = SS + MM * 60 + HH * 3600;

		//是否8点前到,计算提前时间
		if (HH < 8){
			person.ahead_t = 8 * 3600 - person.arr_t;
		}
		else if (HH >= 8){
			person.ahead_t = 0;
		}

		//是否5点后到
		if (person.arr_t > 17 * 3600)	continue;

		//入队
		bank_queue.push_back(person);
	}

	//按时间排序
	sort(bank_queue.begin(), bank_queue.end(), greater_cmp);

	//while (!bank_queue.empty()){
	//	struct Person &p = bank_queue.front();
	//	bank_queue.pop_front();
	//	printf("p.ahead_t: %d p.wait_t: %d p.serve_t: %d p.serving_t: %d p.arr_t: %d\n", p.ahead_t, p.wait_t, p.serve_t, p.serving_t, p.arr_t);
	//}

	//开始服务
	queue_front = bank_queue.size() - 1; //设置队首
	for (;;){
		//记录柜台空置数量
		int null_cnt = 0; 

		//进入柜台
		for (int i = 0; i < K; i++){
			//柜台有空位，队伍不空，进入
			if (counter[i] == -1){
				null_cnt++;
				//队伍不空
				if (queue_front >= 0 && bank_queue[queue_front].arr_t <= gwclock){
					counter[i] = queue_front;//柜台记录进入person编号
					queue_front--; // 出队
				}
			}
		}

		//柜台、队列全空，退出循环
		if (null_cnt == K && queue_front < 0) break;

		//不空的柜台，时间过去1秒。时间到的出柜台
		for (int i = 0; i < K; i++){
			if(counter[i] != -1){
				struct Person &person = bank_queue[counter[i]];
				person.serving_t--;
				if (person.serving_t == 0) counter[i] = -1;
			}
		}

		//队列里小于gwclock的wait_t++
		for (int i = 0; i <= queue_front; i++){
			if (bank_queue[i].arr_t <= gwclock)	bank_queue[i].wait_t++;
		}

		//总时间++
		gwclock++;

	}


	//输出
	//printf("\n");
	vector<Person>::iterator it;
	for (it = bank_queue.begin(); it != bank_queue.end(); it++){
		//计算等待时间+早到时间
		int t = it->wait_t + it->ahead_t;
		total_wait += t;
		//printf("%d %.1lf\n", it->serve_t/60, t/60.0);
	}

	//printf("%d\n", total_wait);
	//printf("size:%d\n", bank_queue.size());
	printf("%.1lf\n", (double)total_wait /60.0/ bank_queue.size());
	




	return 0;
}