/*
 * nbp.cpp
 *
 *  Created on: 2012-11-6
 *      Author: Lsj
 */
int main(){
	int n,i;//??????n?i
	cin>>n;
	int a[1000],b[1000],p[1000]={0};//????
	for(i=0;i<n;i++)
		cin>>a[i]>>b[i];//???a[]?b[]??
	if(a[0]>=90&&a[0]<=140&&b[0]>=60&&b[0]<=90)
		p[0]=1;
	else
		p[0]=0; //???????????????p[0]=1????0
	for(i=1;i<n;i++){
		if(a[i]>=90&&a[i]<=140&&b[i]>=60&&b[i]<=90)
				p[i]=1+p[i-1];
			else
				p[i]=0;//????????????????????p????????0
	}
	for(i=1;i<n;i++){
		if(p[i]<p[i-1])
			p[i]=p[i-1];
	}//?p[]?????
	cout<<p[n-1];//??p????
	return 0;
}