//
//1017. Queueing at Bank (25)
//	accept
#include <iostream>
#include <algorithm>
	using namespace std;

typedef struct 
{
	int second;
	int time;
}Record;


bool cmp(Record r1, Record r2)
{
	if (r1.second == r2.second)
	{
		return r1.time < r2.time;
	}
	return r1.second < r2.second;
}
int main()
{
	int n;
	int k;
	Record r[10005];
	cin >> n >> k;

	int waitingtime = 0;
	int curr[105];


	int len = n;

	int i;

	int h, m, s;

	int index = 0;
	for (i = 0;i<n;i++)
	{
		scanf("%d:%d:%d %d", &h, &m, &s, &r[index].time);
		r[index].second = h * 60 * 60  + m * 60 + s;


		if (r[index].second > 61200)
		{
			index--;
			len--;
		}
		index++;
	}


	fill(curr, curr+k, 8*60*60);
	sort(r, r+len, cmp);

	int start = 0;

	for (i = start; i< start + k && i< len; i++ )
	{
		if (r[i].second < curr[i - start])
		{
			waitingtime += curr[ i- start ] - r[i].second;
			curr[i - start] = curr[i-start] + (r[i].time * 60) ;
		}
		else
		{
			curr[i-start] = r[i].second + (r[i].time * 60);
		}
	}

	i+=start;

	sort(curr, curr+k);
	while( i < len)
	{
		if (r[i].second < curr[0])
		{
			waitingtime += curr[0] - r[i].second;
			curr[0] = curr[0] + (r[i].time * 60) ;
		}
		else
		{
			curr[0] = r[i].second + (r[i].time * 60);
		}
		sort(curr, curr+k);
		i++;
	}
	printf("%.1f", waitingtime / len / 60.0);
	return 0;
}