#region いつもの
#pragma warning disable
using System;
using System.Collections.Generic;
using System.Linq;
using IEnumerable = System.Collections.IEnumerable;
using IEnumerator = System.Collections.IEnumerator;
using BitArray = System.Collections.BitArray;
using BigInteger = System.Numerics.BigInteger;
using TextReader = System.IO.TextReader;
using static AtCoderProject.Global;

namespace AtCoderProject
{
    static class Global
    {
        private class ComparerReverseImpl<T> : Comparer<T> where T : IComparable<T> { public override int Compare(T y, T x) => x.CompareTo(y); public override bool Equals(object obj) => obj != null && GetType() == obj.GetType(); public override int GetHashCode() => GetType().GetHashCode(); }
        public static IComparer<T> ComparerReverse<T>() where T : IComparable<T> => new ComparerReverseImpl<T>();
        public static BigInteger ParseBigInteger(string s)
        {
            // MonoのBigInteger.Parseが遅いので自前実装
            var res = BigInteger.Zero;
            var splited = new string[(s.Length + 7) / 8];
            for (int i = 0; i < splited.Length - 1; i++)
            {
                splited[i] = s.Substring(8 * i, 8);
            }
            splited[splited.Length - 1] = s.Substring(8 * (splited.Length - 1));
            foreach (var sp in splited)
            {
                res *= (int)Math.Pow(10, sp.Length);
                res += int.Parse(sp);
            }
            return res;
        }
        public static string AllLines<T>(IEnumerable<T> source) => string.Join("\n", source);
        public static string AllJoin<T>(IEnumerable<T> source) => string.Join(" ", source);
    }
    static class Ext
    {
        public static IComparer<T> Reverse<T>(this IComparer<T> comparer) => Comparer<T>.Create((x, y) => comparer.Compare(y, x));
        public static Dictionary<TKey, int> GroupCount<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) => source.GroupBy(keySelector).ToDictionary(g => g.Key, g => g.Count());
        public static Dictionary<TKey, int> GroupCount<TKey>(this IEnumerable<TKey> source) => source.GroupCount(i => i);
    }
    public class ConsoleReader { private string[] ReadLineSplit() => textReader.ReadLine().Split(Array.Empty<char>(), StringSplitOptions.RemoveEmptyEntries); private string[] line = Array.Empty<string>(); private int linePosition; private TextReader textReader; public ConsoleReader(TextReader tr) { textReader = tr; } public int Int => int.Parse(String); public int Int0 => Int - 1; public long Long => long.Parse(String); public double Double => double.Parse(String); public string String { get { if (linePosition >= line.Length) { linePosition = 0; line = ReadLineSplit(); } return line[linePosition++]; } } public class SplitLine { private string[] splited; public SplitLine(ConsoleReader cr) { splited = cr.ReadLineSplit(); cr.line = Array.Empty<string>(); } public int[] Int => String.Select(x => int.Parse(x)).ToArray(); public int[] Int0 => String.Select(x => int.Parse(x) - 1).ToArray(); public long[] Long => String.Select(x => long.Parse(x)).ToArray(); public double[] Double => String.Select(x => double.Parse(x)).ToArray(); public string[] String => splited; } public SplitLine Split => new SplitLine(this); public class RepeatReader : IEnumerable<ConsoleReader> { ConsoleReader cr; int count; public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; } public IEnumerator<ConsoleReader> GetEnumerator() => Enumerable.Repeat(cr, count).GetEnumerator(); System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => GetEnumerator(); public IEnumerable<string> String => this.Select(cr => cr.String); public IEnumerable<int> Int => this.Select(cr => cr.Int); public IEnumerable<int> Int0 => this.Select(cr => cr.Int - 1); public IEnumerable<long> Long => this.Select(cr => cr.Long); public IEnumerable<double> Double => this.Select(cr => cr.Double); } public RepeatReader Repeat(int count) => new RepeatReader(this, count); }
    public class Program
    {
        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)] private ConsoleReader consoleReader;
        public Program(ConsoleReader consoleReader) { this.consoleReader = consoleReader; }
        static void Main() => Console.WriteLine(new Program(new ConsoleReader(Console.In)).Calc());

        #endregion
        public object Calc()
        {
            var N = consoleReader.Int;
            var M = consoleReader.Int;
            var P = consoleReader.Int;
            var edges = consoleReader.Repeat(M).Select(cr => new[] { cr.Int - 1, cr.Int - 1, -(cr.Int - P) }).ToArray();

            {
                var gb = new GraphBuilder(N, true);
                foreach (var e in edges)
                    gb.Add(e[0], e[1], e[2]);
                var graph = gb.ToArray();

                var canReach = new HashSet<int>();
                var canGoal = new HashSet<int>();

                var queue = new Queue<int>();

                queue.Enqueue(0);
                canReach.Add(0);
                while (queue.Count > 0)
                {
                    var cur = queue.Dequeue();
                    foreach (var n in graph[cur].children)
                    {
                        var next = n.to;
                        if (canReach.Add(next))
                        {
                            queue.Enqueue(next);
                        }
                    }
                }

                queue = new Queue<int>();
                queue.Enqueue(N - 1);
                canGoal.Add(N - 1);
                while (queue.Count > 0)
                {
                    var cur = queue.Dequeue();
                    foreach (var n in graph[cur].roots)
                    {
                        var next = n.to;
                        if (canGoal.Add(next))
                        {
                            queue.Enqueue(next);
                        }
                    }
                }
                canReach.IntersectWith(canGoal);

                edges = edges.Where(e => canReach.Contains(e[0]) && canReach.Contains(e[1])).ToArray();
            }

            var vertices = new Vertice[N];
            for (int i = 0; i < vertices.Length; i++)
            {
                vertices[i].distance = int.MaxValue / 2;
                vertices[i].predecessor = -1;
            }
            vertices[0].distance = 0;

            for (int i = 0; i < N; i++)
                foreach (var e in edges)
                {
                    var from = e[0];
                    var to = e[1];
                    var weight = e[2];
                    if (vertices[to].distance > vertices[from].distance + weight)
                    {
                        vertices[to].distance = vertices[from].distance + weight;
                        vertices[to].predecessor = from;
                    }
                }

            foreach (var e in edges)
            {
                var from = e[0];
                var to = e[1];
                var weight = e[2];
                if (vertices[to].distance > vertices[from].distance + weight)
                    return -1;
            }

            return Math.Max(-vertices[N - 1].distance, 0);
        }


        struct Vertice
        {
            public int distance;
            public int predecessor;
        }

        class GraphBuilder
        {
            private List<Next>[] roots;
            private List<Next>[] children;
            public GraphBuilder(int count, bool isOriented = true)
            {
                this.roots = new List<Next>[count];
                this.children = new List<Next>[count];
                for (int i = 0; i < count; i++)
                {
                    if (isOriented)
                    {
                        this.roots[i] = new List<Next>();
                        this.children[i] = new List<Next>();
                    }
                    else
                    {
                        this.roots[i] = this.children[i] = new List<Next>();
                    }
                }
            }
            public GraphBuilder(int count, ConsoleReader cr, int edgeCount, bool isOriented = true) : this(count, isOriented)
            {
                for (int i = 0; i < edgeCount; i++)
                    this.Add(cr.Int - 1, cr.Int - 1, cr.Int);
            }
            public void Add(int from, int to, int length)
            {
                children[from].Add(new Next { to = to, length = length });
                roots[to].Add(new Next { to = from, length = length });
            }
            public Node[] ToArray() =>
                Enumerable
                .Zip(roots, children, (r, c) => Tuple.Create(r, c))
                .Select((t, i) => new Node(i, t.Item1.ToArray(), t.Item2.ToArray()))
                .ToArray();

        }
        public struct Next
        {
            public int to;
            public int length;
            public override string ToString() => $"to: {to} length:{length}";
        }
        public class Node : IEquatable<Node>
        {
            public Node(int i, Next[] roots, Next[] children)
            {
                this.index = i;
                this.roots = roots;
                this.children = children;
            }
            public int index;
            public Next[] roots;
            public Next[] children;

            public override bool Equals(object obj)
            {
                if (obj is Node)
                    return this.Equals((Node)obj);
                else
                    return false;
            }
            public bool Equals(Node other) => this.index == other.index;
            public override int GetHashCode() => this.index;
            public override string ToString() => $"children: ({string.Join("),(", children)})";
        }


    }
}


Measured memory_bytes: 16736