#include<stdio.h>
//#include<iostream>
#include<stdlib.h>//malloc?
#include<iomanip>//setprecision(1) 保留一位小数
#define ERROR 0
#define MAX 10000
//using namespace std;
//定义元素类型customer
struct customer{int time_arrive;//以秒计 同下 int time_done;//int time_processing;//int time_remain;//余下时间，开始=processing
};int cmp ( const void *a , const void *b )
{return (*(struct customer *)a).time_arrive >(*(struct customer *)b).time_arrive?1:-1;
}bool winava(struct customer* win[],int k){for(int i=0;i<k;i++){if(win[i]==NULL)return true;}return false;
}int MyMin(struct customer* win[],int k){//当窗口都没有人时返回最大值 int min=60*61;while(k--){if(win[k]!=NULL&&min>win[k]->time_remain)min=win[k]->time_remain;}return min;
}bool clear(struct customer* win[],int k){for(int i=0;i<k;i++)if(win[i]!=NULL)return 0;return 1;
}
int main(){double ave;int n,k,axis=28800,h,m,s,process,order=0;//n:cus,k:windows order记录以处理的客户 0开始 scanf("%d%d",&n,&k);struct customer cus[100010];for(int i=0;i<n;i++){scanf("%d:%d:%d",&h,&m,&s);scanf("%d",&process);if(60*60*h+m*60+s>61200){//晚于17点 n--;i--;continue;}cus[i].time_arrive=60*60*h+m*60+s;//以秒计时 cus[i].time_remain=cus[i].time_processing=process*60;cus[i].time_done=0;}qsort(cus,n,sizeof(struct customer),cmp);//按到达时间排序 struct customer* win[10000];for(int i=0;i<k;i++)win[i]=NULL;while(!(order==n&&clear(win,k))){//order==n时表示队列空 int min=MyMin(win,k);if(order!=n&&(cus[order].time_arrive-axis<min)&&winava(win,k)){//队首到达-axis<min(窗口)&&窗口有空 order==n时表示队列空  出队 if(axis<cus[order].time_arrive){//for(int i=0;i<k;i++){if(win[i])win[i]->time_remain-=(cus[order].time_arrive-axis);}axis=cus[order].time_arrive;}for(int i=0;i<k;i++){if(win[i]==NULL){win[i]=&cus[order];break;}}order++;} else{//处理一个 axis+=min;for(int i=0;i<k;i++){if(win[i]!=NULL&&min==win[i]->time_remain){win[i]->time_done=axis;//cout<<win[i]->time_done/60/60<<":"<<win[i]->time_done/60%60<<endl;win[i]=NULL;}else if(win[i]!=NULL){win[i]->time_remain-=min;} }}}int sum=0;for(int i=0;i<n;i++){sum+=cus[i].time_done-cus[i].time_arrive-cus[i].time_processing;}ave=1.0*sum/60/n;printf("%0.1f",ave);//return 0;
}