#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
using ll = long long;
using P = pair<int, int>;
const ll INF = 1e18;

ll dp[2005][2005];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int n; cin >> n;
    vector<P> p(n);
    for(int i = 0; i < n; i++){
        int a, b; cin >> a >> b;
        p[i] = P(b, a);
    }
    // bの降順にしたい
    sort(p.begin(), p.end(), greater<P>());
    vector<ll> a, b;
    for(auto [x, y]: p){
        a.push_back(y);
        b.push_back(x);
    }
    for(int i = 0; i <= n; i++){
        for(int j = 0; j <= n; j++){
            dp[i][j] = INF;
        }
    }
    dp[0][0] = 0;
    for(int i = 0; i < n; i++){
        for(int j = 0; j <= i; j++){
            // 普通に買う
            chmin(dp[i+1][j], dp[i][j]+a[i]+b[i]*(i-j));
            // ただで買う
            chmin(dp[i+1][j+1], dp[i][j]);
        }
    }
    int x = 0, y = 0;
    int rem = n;
    for(int i = 0; i < n; i++){
        if(i%2 == 0){
            rem--;
            x++;
        }else{
            rem--;
            x++;
            if(rem > 0){
                rem--; y++;
            }
        }
        if(rem == 0) break;
    }
    cout << dp[n][y] << endl;
}