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, a) = (c[0], c[1], c[2]);
        var map = NArr(m);
        var tree = new List<(int to, int p)>[n + 1];
        for (var i = 0; i < tree.Length; ++i) tree[i] = new List<(int to, int p)>();
        foreach (var edge in map)
        {
            tree[edge[0] - 1].Add((edge[1], edge[2]));
        }
        var INF = long.MinValue / 2;
        var dp = Enumerable.Repeat(INF, n + 1).ToArray();
        dp[0] = 0;
        dp[n] = 0;
        var max = 0L;
        for (var i = 0; i < n; ++i)
        {
            if (i > 0) dp[i] = Math.Max(dp[i], max - a);
            foreach (var next in tree[i])
            {
                if (next.to == n) dp[n] = Math.Max(dp[n], dp[i] + next.p);
                else dp[next.to] = Math.Max(dp[next.to], dp[i] + next.p - a);
            }
            max = Math.Max(max, dp[i]);
        }
        WriteLine(Math.Max(dp[n], max));
    }
}