/*
 *????????.cpp
 *?????
 *????: 2012-10-20
 *?????????????????????90 - 140????????60 - 90????????????????????????????????????????????????
 */


int main(){
	int n,sp,dp;					//?????sp,???dp
	int i,time,max;				//??????i???????time,????max
	time = 0;
	max = 0;
	i = 1;
	cin >> n;
	while (i <= n)
	{
		cin >> sp >> dp;
		if(sp >= 90 && sp <= 140 && dp >= 60 && dp <= 90)
		{
			time = time + 1;
		}
		else
		{	if(max<time)
			max = time;
			time = 0;
		}
		if (time > max)
			max = time;
		i = i + 1;
	}
	cout << max;
	return 0;
}