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 c = NList;
        var (n, m) = (c[0], c[1]);
        var map = NArr(m);
        var pt = new long[n];
        foreach (var edge in map)
        {
            pt[edge[0] - 1] += edge[2];
            pt[edge[1] - 1] += edge[2];
        }
        Array.Sort(pt, (l, r) => r.CompareTo(l));
        var ans = 0L;
        for (var i = 0; i < n; ++i)
        {
            if (i % 2 == 0) ans += pt[i];
            else ans -= pt[i];
        }
        WriteLine(ans / 2);
    }
}