#include<bits/stdc++.h>
using namespace std;
int n;
struct food{
	bool x;
	int y;
	void input(){
		cin>>x>>y;
	}
};
food a[300005];
int dfs(int i,int j){
	if(i == 1)return a[i].y;
	if(a[i].y==0)return dfs(i-1,j)+a[i].y; 
	else if(j == 0){
		if(a[i].x)return dfs(i-1,1)+a[i].y;
		else return dfs(i-1,0)+a[i].y;
	}else{
		if(a[i].x)return dfs(i-1,1);
		else return dfs(i-1,0)+a[i].y;
	}
}
int main(){
	cin>>n;
	for(int i = 1;i<=n;i++){
		a[i].input();
	}
	cout<<max(dfs(n,0),0);
}

大佬求捞