#include<algorithm>
#include<complex>
#include<ctype.h>
#include<iomanip>
#include<iostream>
#include<fstream>
#include<map>
#include<math.h>
#include<numeric>
#include<queue>
#include<set>
#include<stack>
#include<stdio.h>
#include<string>
#include<string>
#include<vector>

using namespace std;
typedef long long ll;

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

struct Item{
    ll a;
    ll b;
    Item(ll _a, ll _b){
        a = _a;
        b = _b;
    }

    static bool sortByB(Item s, Item t){
        return s.b < t.b;
    }

    string ToString(){
        stringstream ss;
        ss << "item " << a << " " << b;
        return ss.str();
    }
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N;
    cin >> N;

    vector<Item> A;
    FOR(i, 0, N){
        ll a, b;
        cin >> a >> b;
        A.push_back(Item(a, b));
    }
    sort(ALL(A), Item::sortByB);
    reverse(ALL(A));

    ll dp[N+1][N+1];
    FOR(i, 0, N+1){
        FOR(j, 0, N+1){
            dp[i][j] = -1;
        }
    }

    FOR(i, 0, N+1){
        dp[0][i] = 0;
    }

    // j==0
    FOR(i, 1, N+1){
        dp[i][0] = dp[i-1][0] + A[i-1].a + A[i-1].b * (i-1);
    }

    FOR(i, 1, N+1){
        FOR(j, 1, N+1){
            ll t = i - j - 1;
            if(t<0){
                dp[i][j] = 0;
            }else{
                dp[i][j] = min(dp[i-1][j-1], dp[i-1][j] + A[i-1].a + A[i-1].b * t);
            }
        }
    }

    ll a = dp[N][N/3];
    p(a);
    
    return 0;
}