#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;

const int nn=100005;
const int kk=1440;
const int mod=999979;

int n,k;
struct node{
	int num;
	//char id[18];
	int time;
}a[nn];
int ans,now;

int b[nn],c[nn];
//int team[nn],head,tail;
queue<int> q;

int Hash(char id[])
{
	int res=0;
	for(int i=0;i<strlen(id);i++)
	{
		res*=mod;res+=id[i];
	}
	res%=mod;
	if(res<0) res+=mod;
	res++;
	return res;
}

int frst[mod+3],nxt[nn],tot;
char go[nn][18];
int Make(int h,char id[],int time)
{
	//printf("make-OK0 time=%d h=%d\n",time,h);    //
	for(int i=frst[h];i;i=nxt[i])
	{
		char v[18];
		for(int j=0;j<18;j++) v[j]=go[i][j];
		
		int jie=0;
		for(int j=0;j<18;j++)
		{
			if(v[j]!=id[j])
			{
				jie=1;
				break;
			}
		}
		if(jie==0)
		{
			//printf("make-f1-if return\n");       //
			return i;
		}
	}
	//printf("make-OK1\n");                        //
	
	tot++;nxt[tot]=frst[h];frst[h]=tot;//go[tot]=id;
	for(int j=0;j<18;j++) go[tot][j]=id[j];
	return tot;
}

bool cmpn(node,node);

int main()
{
	//freopen("switch.in","r",stdin);
	//freopen("switch.out","w",stdout);
	
	scanf("%d%d",&n,&k);
	for(int i=0;i<n;i++)
	{
		//printf("m-f1-OK0 i=%d\n",i);             //
		char id[18];
		int hour,minute;
		scanf("%s",id);
		//printf("m-f1-OK1 read_id\n");            //
		scanf("%d:%d",&hour,&minute);
		a[i].time=hour*60+minute;
		//printf("m-f1-OK2\n");                    //
		
		int x=Hash(id);
		//printf("m-f1-OK3\n");                    //
		
		a[i].num=Make(x,id,a[i].time);
	}
	
	sort(a,a+n,cmpn);
	
	q.push(a[0].num);
	b[a[0].num]=1;
	now=1;
	for(int head=0,tail=0;head<=tail;head++)
	{
		for(;tail+1<n;tail++)
		{
			if(a[tail+1].num<a[head].num+k)
			{
				tail++;
				c[a[tail].num]=a[tail].time;
				if(b[a[tail].num]==0)
				{
					b[a[tail].num]=1;
					now++;
				}
			}
		}
		ans=max(now,ans);
		if(c[a[head].num]==a[head].time)
		{
			b[a[head].num]=0;
		}
	}
	
	printf("%d",ans);
	
	return 0;
}
bool cmpn(node x,node y)
{
	if(x.time!=y.time) return x.time<y.time;
	return x.num<y.num;
}