int main()
{
	int n,i,hour,answer,k,p;
	int sys[100];
	int dia[100];
	int hours[100];
	//???????sys???????dia???????hours???????
	scanf("%d",&n);
	for(i=1,k=0,hour=0;i<=n;i++)
	{
		scanf("%d%d",&sys[i],&dia[i]);
		if(sys[i]<=140&&sys[i]>=90&&dia[i]<=90&&dia[i]>=60)
		{
			hour+=1;
			if(hour>k)
				k=hour;
			else
				k=k;
		}
		else
			hour=0;
		hours[i]=hour;
	}
	hours[0]=0;
	for(i=1,answer=0;i<=n;i++)
	{
		if(hours[i]>=hours[i-1])
			answer=hours[i];
		else
			answer=answer;
	}
	answer=k;
	printf("%d\n",answer);
	return 0;
}