#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define int long long
using namespace std;
typedef pair<int, int> P;
const int mod = 1000000007;
const int INF = 1e18;

int dp[2010], nxt[2010];

signed main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    vector<P> d(n);
    rep(i, 0, n){
        cin >> a[i] >> b[i];
        d[i] = {b[i], i};
    }
    sort(d.rbegin(), d.rend());
    int m = n - n / 3;
    for(int i = 0; i <= n; i++) dp[i] = INF;
    dp[0] = 0;
    for(int i = 0; i < n; i++){
        int id = d[i].second;
        for(int j = 0; j <= n; j++) nxt[j] = dp[j];
        for(int j = 0; j < m; j++){
            if(dp[j] == INF) break;
            nxt[j + 1] = min(nxt[j + 1], dp[j] + a[id] + b[id] * j);
        }
        swap(dp, nxt);
    }
    cout << dp[m] << endl;    
}