using System;
using System.CodeDom;
using System.Collections.Generic;
using System.Data.SqlTypes;
using System.IO;
using System.Linq;
using System.Net.Http.Headers;
using System.Runtime.InteropServices;

namespace AtCoder
{
    public static class Ex
    {
        public static bool IsNullOrEmpty(this string s) { return string.IsNullOrEmpty(s); }
        public static List<string> FastSort(this List<string> s) { s.Sort(StringComparer.OrdinalIgnoreCase); return s.ToList(); }
        public static void yesno(this bool b) { Console.WriteLine(b ? "yes" : "no"); }
        public static void YesNo(this bool b) { Console.WriteLine(b ? "Yes" : "No"); }
        public static void YESNO(this bool b) { Console.WriteLine(b ? "YES" : "NO"); }
        public static int PopCount(this int bits)
        {
            bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);
            bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);
            bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);
            bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);
            return (bits & 0x0000ffff) + (bits >> 16 & 0x0000ffff);
        }
    }



    partial class AtCoder
    {
        public string GetStr() { return Console.ReadLine().Trim(); }
        public char GetChar() { return Console.ReadLine().Trim()[0]; }
        public int GetInt() { return int.Parse(Console.ReadLine().Trim()); }
        public long GetLong() { return long.Parse(Console.ReadLine().Trim()); }
        public double GetDouble() { return double.Parse(Console.ReadLine().Trim()); }
        public string[] GetStrArray() { return Console.ReadLine().Trim().Split(' '); }
        public string[][] GetStrArray(int N)
        {
            var res = new string[N][];
            for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ');
            return res;
        }
        public int[] GetIntArray() { return Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray(); }
        public int[][] GetIntArray(int N)
        {
            var res = new int[N][];
            for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray();
            return res;
        }
        public long[] GetLongArray() { return Console.ReadLine().Trim().Split(' ').Select(long.Parse).ToArray(); }
        public long[][] GetLongArray(int N)
        {
            var res = new long[N][];
            for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ').Select(long.Parse).ToArray();
            return res;
        }
        public char[] GetCharArray() { return Console.ReadLine().Trim().Split(' ').Select(char.Parse).ToArray(); }
        public double[] GetDoubleArray() { return Console.ReadLine().Trim().Split(' ').Select(double.Parse).ToArray(); }
        public double[][] GetDoubleArray(int N)
        {
            var res = new double[N][];
            for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ').Select(double.Parse).ToArray();
            return res;
        }
        public char[][] GetGrid(int H)
        {
            var res = new char[H][];
            for (int i = 0; i < H; i++) res[i] = Console.ReadLine().Trim().ToCharArray();
            return res;
        }
        public T[] CreateArray<T>(int N, T value)
        {
            var res = new T[N];
            for (int i = 0; i < N; i++) res[i] = value;
            return res;
        }
        public T[][] CreateArray<T>(int H, int W, T value)
        {
            var res = new T[H][];
            for (int i = 0; i < H; i++)
            {
                res[i] = new T[W];
                for (int j = 0; j < W; j++) res[i][j] = value;
            }
            return res;
        }
        public T[][][] CreateArray<T>(int H, int W, int R, T value)
        {
            var res = new T[H][][];
            for (int i = 0; i < H; i++)
            {
                res[i] = new T[W][];
                for (int j = 0; j < W; j++)
                {
                    res[i][j] = new T[R];
                    for (int k = 0; k < R; k++) res[i][j][k] = value;
                }
            }
            return res;
        }

        Dictionary<int, List<int>> GetUnweightedAdjacencyList(int N, int M, bool isDirected, bool isNode_0indexed)
        {
            var dic = new Dictionary<int, List<int>>();
            foreach (var e in Enumerable.Range(0, N)) { dic.Add(e, new List<int>()); }
            for (int i = 0; i < M; i++)
            {
                var input = GetIntArray();
                var a = isNode_0indexed ? input[0] : input[0] - 1;
                var b = isNode_0indexed ? input[1] : input[1] - 1;
                dic[a].Add(b);
                if (isDirected == false) dic[b].Add(a);
            }
            return dic;
        }
        Dictionary<int, List<Edge>> GetWeightedAdjacencyList(int N, int M, bool isDirected, bool isNode_0indexed)
        {
            var dic = new Dictionary<int, List<Edge>>();
            foreach (var e in Enumerable.Range(0, N)) { dic.Add(e, new List<Edge>()); }
            for (int i = 0; i < M; i++)
            {
                var input = GetIntArray();
                var a = isNode_0indexed ? input[0] : input[0] - 1;
                var b = isNode_0indexed ? input[1] : input[1] - 1;
                var c = input[2];
                dic[a].Add(new Edge(b, c));
                if (isDirected == false) dic[b].Add(new Edge(a, c));
            }
            return dic;
        }

        bool eq<T, U>() => typeof(T).Equals(typeof(U));
        T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
        T cv<T>(string s) => eq<T, int>() ? ct<T, int>(int.Parse(s))
                           : eq<T, long>() ? ct<T, long>(long.Parse(s))
                           : eq<T, double>() ? ct<T, double>(double.Parse(s))
                           : eq<T, char>() ? ct<T, char>(s[0])
                                             : ct<T, string>(s);
        void Multi<T>(out T a) => a = cv<T>(GetStr());
        void Multi<T, U>(out T a, out U b)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]);
        }
        void Multi<T, U, V>(out T a, out U b, out V c)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]);
        }
        void Multi<T, U, V, W>(out T a, out U b, out V c, out W d)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]);
        }
        void Multi<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]);
        }
        void Multi<T, U, V, W, X, Y>(out T a, out U b, out V c, out W d, out X e, out Y f)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]); f = cv<Y>(ar[5]);
        }

        int[] dx = new int[] { 1, 0, -1, 0, 1, 1, -1, -1 };
        int[] dy = new int[] { 0, 1, 0, -1, 1, -1, 1, -1 };
    }

    class Pair : IComparable<Pair>
    {
        public Pair(int node, long cost)
        {
            Node = node; Cost = cost;
        }
        public int Node { get; set; }
        public long Cost { get; set; }
        public int CompareTo(Pair p)
        {
            return p.Cost > Cost ? 1 : -1;
        }
    }

    class Edge
    {
        public Edge(int to, long length)
        {
            To = to;
            Length = length;
        }
        public int To { get; set; }
        public long Length { get; set; }
    }

    class Comparable : IComparable<Comparable>
    {
        public Comparable(int value)
        {
            Value = value;
        }

        public int Value { get; set; }
        public int CompareTo(Comparable c)
        {
            var a = Math.Abs(Value);
            var b = Math.Abs(c.Value);
            return a > b ? 1 : a == b ? 0 : -1;
        }
    }

    class Comparer<T> : IComparer<T>
    {
        public int Compare(T t1, T t2)
        {
            return 1;
        }
    }



    partial class Program
    {
        static void Main()
        {
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
            new AtCoder().Solve();
            Console.Out.Flush();
            Console.Read();
        }
    }

    public partial class AtCoder
    {
        public void Solve()
        {
            int H, W, K;
            Multi(out H, out W, out K);
            var item = CreateArray(H, W, 0L);
            for (int i = 0; i < K; i++)
            {
                int y, x; long v;
                Multi(out y, out x, out v);
                y--; x--;
                item[y][x] = v;
            }

            var dp = CreateArray(4, H + 1, W + 1, long.MinValue);
            dp[0][0][1] = 0;

            for (int y = 0; y < H; y++)
            {
                for (int x = 0; x < W; x++)
                {
                    var value = item[y][x];
                    var max = Math.Max(Math.Max(dp[0][y][x + 1], dp[1][y][x + 1]), Math.Max(dp[2][y][x + 1], dp[3][y][x + 1]));
                    dp[0][y + 1][x + 1] = Math.Max(max, dp[0][y + 1][x]);
                    dp[1][y + 1][x + 1] = Math.Max(Math.Max(dp[1][y + 1][x], dp[0][y + 1][x] + value), max + value);
                    dp[2][y + 1][x + 1] = Math.Max(dp[2][y + 1][x], dp[1][y + 1][x] + value);
                    dp[3][y + 1][x + 1] = Math.Max(dp[3][y + 1][x], dp[2][y + 1][x] + value);
                }
            }
            Console.WriteLine(Enumerable.Range(0, 4).Select(i => dp[i][H][W]).Max());
        }
    }
}


Measured memory_bytes: 383512