#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>

using namespace std;

#define int long long
#define rep(i,n) for(int i = 0; i < (n); i++)
#define INF ((long long)1e18)
#define MOD ((int)1e9+7)
#define endl "\n"

#define yn(f) ((f)?"Yes":"No")
#define YN(f) ((f)?"YES":"NO")

#define MAX 2100

int dp[MAX][MAX];

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);
	
	int N, con;
	pair<int,int> AB[MAX];
	
	cin>>N;
	
	for(int i = 0; i < N; i++){
		cin>>AB[i].second>>AB[i].first;
	}
	
	sort(AB, AB+N, greater<pair<int,int>>());
	for(int i = 1; i <= N; i++){
		for(int j  = 0; j <= N/3 && j < i; j++){
			dp[i][j] = INF;
		}
	}
	
	
	for(int i = 1; i <= N; i++){
		for(int j  = 0; j <= N/3 && j < i; j++){
			if(j)dp[i][j] = min(dp[i-1][j-1], dp[i-1][j] + AB[i-1].second + AB[i-1].first*(i-j-1));
			else dp[i][j] = dp[i-1][j] + AB[i-1].second + AB[i-1].first*(i-j-1);
			// if(j)cout<<i<<" "<<j<<" "<<dp[i-1][j-1]<<" "<<dp[i-1][j] + AB[i-1].second + AB[i-1].first*(i-j-1)<<endl;
			// else cout<<i<<" "<<j<<" "<<"--- "<<dp[i-1][j] + AB[i-1].second + AB[i-1].first*(i-j-1)<<endl;
		}
	}
	cout<<dp[N][N/3]<<endl;
	
	return 0;
}