#include <bits/stdc++.h>
using namespace std;

int n;
pair<long long, long long> p[3000];

long long memo[2010][2010];

long long dp(long long i, int nk, int cnt){
    if(i == n){
        return 0;
    }

    if(memo[i][nk] != -1) return memo[i][nk];

    long long ans = dp(i+1, nk, cnt+1) + p[i].first * cnt + p[i].second;
    if(nk > 0){
        ans = min(ans, dp(i+1, nk-1, cnt));
    }

    return memo[i][nk] = ans;
}

int main(){
    cin >> n;

    for(int i = 0;i < n;i++){
        cin >> p[i].second >> p[i].first;
    }

    sort(p, p+n, greater<pair<long long, long long> >());

    memset(memo, -1, sizeof(memo));

    cout << dp(0, n/3, 0) << endl;

    return 0;
}