#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b)*b; }
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T> V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T> mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }

/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

ll dp[2020][2020];
template<class Type>
Type solve(Type res = Type()){
    ll N; cin >> N;
    vector<pll> AB(N);
    for(int i = 0; i < N;i++){
        ll A,B; cin >> A >> B;
        AB[i] = {B,A};
    }
    sort(AB.rbegin(),AB.rend());
    fill(*dp,*dp+2020*2020,LINF);
    dp[0][0] = 0;
    for(int i = 0; i < N;i++){
        ll A,B; tie(B,A) = AB[i];
        for(int j = 0; j <= i;j++){
            if(dp[i][j]==LINF) continue;
            // 無料でもらう
            dp[i+1][j+1] = min(dp[i+1][j+1],dp[i][j]);
            // 購入
            dp[i+1][j] = min(dp[i+1][j],dp[i][j]+A+B*((i+1)-j-1));
        }
    }
    res = dp[N][N/3];
    return res;
}
int main(void) {
    cin.tie(0); ios::sync_with_stdio(false);
    //solve<ll>(0);
    cout << fixed << setprecision(12) << solve<ll>() << endl;
    return 0;
}