#include<bits/stdc++.h>
using namespace std;
struct l{
	int l,r;
}tre[10000001];
int main()
{
	int n,x=1,sa=1;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>tre[i].l>>tre[i].r;
		if(tre[i].l!=0&&tre[i].r!=0)
		{
			x++;
			sa++;
		}
		else if (tre[i].l!=0||tre[i].r!=0)x++;
		else sa--;
	}
	cout<<x;
	return 0;
}