using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
using System.Runtime.Intrinsics.Arm;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var map = NArr(n);
        Array.Sort(map, (l, r) => r[1].CompareTo(l[1]));
        var buy = n - n / 3;
        var INF = long.MaxValue / 2;
        var dp = Enumerable.Repeat(INF, buy + 1).ToArray();
        dp[0] = 0;
        for (var i = 0; i < n; ++i)
        {
            for (var j = buy - 1; j >= 0; --j)
            {
                if (dp[j] == INF) continue;
                dp[j + 1] = Math.Min(dp[j + 1], dp[j] + map[i][0] + map[i][1] * j);
            }
        }
        WriteLine(dp[^1]);
    }
}