#include<bits/stdc++.h> 
using namespace std;
int n;
int a[1000010]={0};
int b[1000010]={0};
int c[1000010]={0};

int dg(int x)
{
	int ans,ans1,ans2,i;
	if(x>n)
	{
		return 0;
	}
	ans1=0+dg(x+1);
	c[b[x]]=-1;
	c[x]=1;
	for(i=x+1;i<=n;i++)
	{
		if(c[i]!=-1&&b[i]!=1)
		{
			break;
		}
	}
	if(i>n)
	{
		ans2=a[x];
	}
	else
	{
    	ans2=a[x]+dg(i);
	}
	ans=max(ans1,ans2);
	return ans;
}
int main()
{
    freopen("bzoj_1040.in","r",stdin);
    freopen("bzoj_1040.out","w",stdout);
    int x,y,z,i,j;
    cin>>n;
    for(i=1;i<=n;i++)
    {
		cin>>a[i]>>b[i];
	}
	cout<<dg(1);
    return 0;
}