int main(){
	int i,n,t=0,b=0,max[110],min[110];
	scanf("%d",&n);
	for(i=0;i<n;i++){
		scanf("%d%d",&max[i],&min[i]);
	}
	if(max[0]>=90&&max[0]<=140&&min[0]>=60&&min[0]<=90){
		t++;
		b=t;
		}
	for(i=1;i<n;i++){
	    if(max[i]>=90&&max[i]<=140&&min[i]>=60&&min[i]<=90){
			if(max[i-1]>=90&&max[i-1]<=140&&min[i-1]>=60&&min[i-1]<=90){
				t++;
				if(t>b){b=t;}
			}else{
				t=0;
				t++;
                if(t>b){b=t;}
			}
		}else{
			if(max[i-1]>=90&&max[i-1]<=140&&min[i-1]>=60&&min[i-1]<=90){
				if(t>b){
					b=t;
					t=0;
				}
			}
		}
	}
	printf("%d",b);
	return 0;
}