#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int n,a[2000],b[2000];
main()
{
	cin>>n;
	for(int i=0;i<n;i++)cin>>a[i]>>b[i];
	int k=0;
	while(k+k/2<n)k++;
	vector<pair<int,int> >x;
	for(int i=0;i<n;i++)x.push_back(make_pair(b[i],a[i]));
	for(int ccc=0;ccc<n-k;ccc++)
	{
		sort(x.begin(),x.end());
		int sum=0;
		vector<pair<int,int> >de;
		for(int i=0;i<x.size();i++)
		{
			int now=x[i].second+x[i].first*(x.size()-i-1);
			de.push_back(make_pair(sum+now,i));
			sum+=x[i].first;
		}
		sort(de.begin(),de.end());
		vector<pair<int,int> >::iterator it=x.begin();
		for(int i=0;i<de[de.size()-1].second;i++)it++;
		x.erase(it);
	}
	long ans=0;
	sort(x.begin(),x.end());
	for(int i=0;i<x.size();i++)ans+=x[x.size()-i-1].second+x[x.size()-i-1].first*i;
	cout<<ans<<endl;
}