using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

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);
        {
            var set = new HashSet<int>() { 0 };
            for (var i = 0; i < n; ++i) set.Add(map[i][0]);
            var list = new List<int>(set);
            list.Sort();
            var dic = new Dictionary<int, int>();
            for (var i = 0; i < list.Count; ++i) dic[list[i]] = i;
            for (var i = 0; i < n; ++i) map[i][0] = dic[map[i][0]];
        }
        {
            var set = new HashSet<int>() { 0 };
            for (var i = 0; i < n; ++i) set.Add(map[i][1]);
            var list = new List<int>(set);
            list.Sort();
            var dic = new Dictionary<int, int>();
            for (var i = 0; i < list.Count; ++i) dic[list[i]] = i;
            for (var i = 0; i < n; ++i) map[i][1] = dic[map[i][1]];
        }
        var lists = new List<int[]>[n + 1];
        for (var i = 0; i < lists.Length; ++i) lists[i] = new List<int[]>();
        for (var i = 0; i < n; ++i) lists[map[i][0]].Add(map[i]);
        var seg = new AtCoder.Segtree<int, SegOp>(n + 1);
        for (var i = 0; i < lists.Length; ++i)
        {
            var add = new List<(int b, int c)>();
            foreach (var li in lists[i])
            {
                add.Add((li[1], seg.Prod(0, li[1]) + li[2]));
            }
            foreach (var ai in add) seg[ai.b] = Math.Max(seg[ai.b], ai.c);
        }
        WriteLine(seg.AllProd);
    }
    struct SegOp : AtCoder.ISegtreeOperator<int>
    {
        public int Identity => 0;

        public int Operate(int x, int y)
        {
            return Math.Max(x, y);
        }
    }
}