#include<bits/stdc++.h>

using namespace std;

const int N = 1e5 + 10;
struct node {
	string s;
	int t;
} a[N];

int n, k;
queue<int> q;
map<string, int> mpTime, inQueue;


int main(){
	cin >> n >> k;
	for (int i = 1; i <= n; i++) {
		cin >> a[i].s;
		int h, m; char ch;
		cin >> h >> ch >> m;
		a[i].t = h * 60 + m;
	}
	sort(a + 1, a + n + 1, [](node x, node y) {
		return x.t < y.t;
	});

	int ans = 0;
	for (int i = 1; i <= n; i++) {
		int nowTime = a[i].t;
		while (q.size() && mpTime[a[q.front()].s] + k < nowTime) {
			mpTime[a[q.front()].s] = -k - 1;
			inQueue[a[q.front()].s] = 0;
			q.pop();
		}
		if (!inQueue[a[i].s]) {
			q.push(i);
			inQueue[a[i].s] = 1;
		}
		mpTime[a[i].s] = nowTime;

		ans = max(ans, int(q.size()));
	}
	cout << ans << '\n';
	
	// system("pause");
	return 0;
}