#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <array>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
#include <memory>
#include <regex>
using namespace std;

const long long INF = LLONG_MAX / 2;

int main()
{
    int n;
    cin >> n;
    vector<pair<long long, long long> > v(n);
    for(int i=0; i<n; ++i)
        cin >> v[i].second >> v[i].first;
    sort(v.begin(), v.end());

    int m = n - n / 3;
    vector<long long> dp(m+1, INF);
    dp[0] = 0;
    for(int i=n-1; i>=0; --i){
        for(int j=m-1; j>=0; --j){
            long long cost = v[i].first * j + v[i].second;
            dp[j+1] = min(dp[j+1], dp[j] + cost);
        }
    }
    cout << dp[m] << endl;

    return 0;
}