#pragma GCC optimize ("O3")

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <set>
#include <algorithm>
#include <numeric>
#include <list>
using namespace std;

using QWORD  = uint64_t;
using SQWORD = int64_t;
using DWORD  = uint32_t;
using SDWORD = int32_t;
using WORD   = uint16_t;
using SWORD  = int16_t;
using BYTE   = uint8_t;
using SBYTE  = int8_t;
using DOUBLE = double;
using FLOAT  = float;

#define MIN_SDWORD (-2147483648)
#define MAX_SDWORD (2147483647)
#define MIN_SBYTE (-128)
#define MAX_SBYTE (127)

#define MIN_SQWORD (0x8000000000000000)
#define MAX_SQWORD (0x7FFFFFFFFFFFFFFF)

#define MAX_QWORD  (0xFFFFFFFFFFFFFFFF)
#define MAX_DWORD  (0xFFFFFFFF)
#define MAX_WORD   (0xFFFF)
#define MAX_BYTE   (0xFF)

#define MAX_DOUBLE      (1.0e+308)
#define DOUBLE_EPS      (1.0e-12)
#define MIN_DOUBLE_N    (-1.0e+308)

#define ArrayLength(a)  (sizeof(a) / sizeof(a[0]))

static inline DOUBLE MAX(DOUBLE a, DOUBLE b) { return a > b ? a : b; }
static inline QWORD MAX(QWORD a, QWORD b) { return a > b ? a : b; }
static inline DWORD MAX(DWORD a, DWORD b) { return a > b ? a : b; }
static inline SDWORD MAX(SDWORD a, SDWORD b) { return a > b ? a : b; }
static inline DOUBLE MIN(DOUBLE a, DOUBLE b) { return a < b ? a : b; }
static inline QWORD MIN(QWORD a, QWORD b) { return a < b ? a : b; }
static inline DWORD MIN(DWORD a, DWORD b) { return a < b ? a : b; }
static inline SDWORD MIN(SDWORD a, SDWORD b) { return a < b ? a : b; }

#define BYTE_BITS   (8)
#define WORD_BITS   (16)
#define DWORD_BITS  (32)
#define QWORD_BITS  (64)

static inline void inputStringSpSeparated(char *pcStr)
{
    char *pcCur = pcStr;
    for (;;) {
        char c = getchar();
        if (('\n' == c) || (EOF == c) || (' ' == c)) {
            break;
        }
        *pcCur = c;
        pcCur++;
    }
    *pcCur = '\0';
}

static inline void inputString(char *pcStr)
{
    char *pcCur = pcStr;
    for (;;) {
        char c = getchar();
        if (('\n' == c) || (EOF == c)) {
            break;
        }
        *pcCur = c;
        pcCur++;
    }
    *pcCur = '\0';
}


static inline SQWORD inputSQWORD(void)
{
    SQWORD sqNumber = 0;
    SQWORD sqMultiplier = 1;
    bool bRead = false;
    for (;;) {
        char c = getchar();
        if (!bRead) {
            if ('-' == c) {
                sqMultiplier = -1;
            }
        }
        if (('0' <= c) && (c <= '9')) {
            sqNumber *= 10LL;
            sqNumber += (SQWORD)(c - '0');
            bRead = true;
        } else {
            if (bRead) {
                return sqNumber * sqMultiplier;
            }
        }
    }
}


static inline SDWORD inputSDWORD(void)
{
    SDWORD lNumber = 0;
    SDWORD lMultiplier = 1;
    bool bRead = false;
    for (;;) {
        char c = getchar();
        if (!bRead) {
            if ('-' == c) {
                lMultiplier = -1;
            }
        }
        if (('0' <= c) && (c <= '9')) {
            lNumber *= 10;
            lNumber += (c - '0');
            bRead = true;
        } else {
            if (bRead) {
                return lNumber * lMultiplier;
            }
        }
    }
}

static inline DOUBLE inputFP(void)
{
    DOUBLE dInt = 0.0;
    DOUBLE dFrac = 0.0;
    DOUBLE dMultiplier = 1.0;
    DWORD dwFpCnt = 0;
    DOUBLE *pdCur = &dInt;
    bool bRead = false;
    for (;;) {
        char c = getchar();
        if (!bRead) {
            if ('-' == c) {
                dMultiplier = -1;
            }
        }
        if ('.' == c) {
            pdCur = &dFrac;
        } else if (('0' <= c) && (c <= '9')) {
            (*pdCur) *= 10;
            (*pdCur) += (DOUBLE)(c - '0');
            bRead = true;
            if (pdCur == &dFrac) {
                dwFpCnt++;
            }
        } else {
            if (bRead) {
                return dMultiplier * (dInt + dFrac / (pow((DOUBLE)10.0 , (DOUBLE)dwFpCnt)));
            }
        }
    }
}


/**
 *  mod による操作ライブラリ
 */

#define ANS_MOD (1000000007LL)
 
static SQWORD addMod(SQWORD x, SQWORD y)
{ 
    return (x + y) % ANS_MOD;
}
 
static SQWORD subMod(SQWORD x, SQWORD y)
{
    return (x - y + ANS_MOD) % ANS_MOD;
}
 
static SQWORD mulMod(SQWORD x, SQWORD y) 
{
    return (x * y) % ANS_MOD;
}
 
static SQWORD powMod(SQWORD x, SQWORD e) {
    SQWORD v = 1;
    for (; e; x = mulMod(x, x), e >>= 1) {
        if (e & 1) {
            v = mulMod(v, x);
        }
    }
    return v;
}
 
static SQWORD divMod(SQWORD x, SQWORD y)
{
    return mulMod(x, powMod(y, ANS_MOD - 2));
}
 
 
static SQWORD combMod(SQWORD n, SQWORD k)
{
    SQWORD v=1;
    for(SQWORD i=1; i<=k; i++) {
        v = divMod(mulMod(v, n-i+1),i);
    } 
    return v;
}

/*----------------------------------------------*/

/**
*   ベルマンフォード法
*/
struct Edge {
    SQWORD to;   // 辺の接続先頂点,
    SQWORD cost;   //辺の重み
    Edge(SQWORD to, SQWORD cost) : to(to), cost(cost) {}  // コンストラクタ
};

typedef vector<vector<Edge> > AdjList;  // 隣接リストの型

#define NODE_NUM    (2501)

class BellmanFordGraph {
    const SQWORD UNDEF = (SQWORD)(-100100100100100100);
    const SQWORD INF = (SQWORD)(100100100100100100);

    SQWORD sqNodeNum;
    AdjList graph;                  /* グラフの辺を格納した構造体
                                      graph[v][i]は頂点vから出るi番目の辺Edge */ 
    SQWORD score[NODE_NUM];
    vector<SQWORD> avAdjFwd[NODE_NUM];
    vector<SQWORD> avAdjRev[NODE_NUM];
    bool abPassFwd[NODE_NUM];
    bool abPassRev[NODE_NUM];
    bool abOnPath[NODE_NUM];

private:
    inline void dfs_exec(
        SQWORD sqNode, 
        bool *pbPass, 
        const vector<SQWORD> *pvAdj,
        void (BellmanFordGraph::*pFunc)(SQWORD))
    {
        if (pbPass[sqNode]) {
            return;
        }
        pbPass[sqNode] = true;
        for (auto next: pvAdj[sqNode]) {
            (this->*pFunc)(next);
        }
    }

    void dfs(SQWORD sqNode)
    {
        dfs_exec(sqNode, abPassFwd, avAdjFwd, &BellmanFordGraph::dfs);
    }

    void rdfs(SQWORD sqNode)
    {
        dfs_exec(sqNode, abPassRev, avAdjRev, &BellmanFordGraph::rdfs);
    }

public:
    BellmanFordGraph(SQWORD sqN) 
    {
        sqNodeNum = sqN;
        graph.resize(sqN);
        for (SQWORD sqIdx = 0; sqIdx < sqN; sqIdx++) {
            abPassFwd[sqIdx] = false;
            abPassRev[sqIdx] = false;
            abOnPath[sqIdx]  = true; 
        }
    };

    void AddEdge(SQWORD sqFrom, SQWORD sqTo, SQWORD sqCost) 
    {
        graph[sqFrom].push_back(Edge(sqTo, sqCost));
        avAdjFwd[sqFrom].push_back(sqTo);
        avAdjRev[sqTo].push_back(sqFrom);
    };

    /**
    *   有向グラフで開始点-終了点の間で通過不可能なノードを探す
    *       (呼ばなければ全ノードを探索パスとする)
    */
    void searchUnpassableNode(
        SQWORD sqStart,             /* 開始頂点 */
        SQWORD sqGoal)              /* 到達頂点(閉路検出で使う) */
    {
        /* スタート・ゴールからそれぞれ到達可能なノードを探す */
        dfs(sqStart);
        rdfs(sqGoal);

        for (SQWORD sqNodeIdx = 0; sqNodeIdx < sqNodeNum; sqNodeIdx++) {
            abOnPath[sqNodeIdx] = abPassFwd[sqNodeIdx] && abPassRev[sqNodeIdx];
        }
    };

private:
    void updateBellmanFord(SQWORD sqV, bool &bUpdate)
    {
        if (!abOnPath[sqV]) {
            return;
        }
        for (auto e: graph[sqV]) {
            if ((score[sqV] != UNDEF) 
                && (score[e.to] < score[sqV] + e.cost)) {
                score[e.to] = score[sqV] + e.cost;
                bUpdate = true;
            }
        }
    };

public:

    /**
    *   ベルマンフォード法
    *       ・辺に価値がある変形版
    *       ・戻り値が false なら正の閉路を含む
    */
    bool bellman_ford(
        SQWORD sqStart,             /* 開始頂点 */
        SQWORD sqGoal)              /* 到達頂点(閉路検出で使う) */
    { 
        for (SQWORD sqIdx = 0; sqIdx < sqNodeNum; sqIdx++) {
            score[sqIdx] = UNDEF;
        }
        score[sqStart] = 0;         /* 開始点のスコアは0 */

        bool bErr;
        for (SQWORD i = 0; i <= sqNodeNum; i++) {
            bool bUpdate = false;
            for (int v = 0; v < sqNodeNum; v++) {
                updateBellmanFord(v, bUpdate);
            }
            if ((sqNodeNum - 1 < i) && bUpdate) {
                return false;
            }
        }
        return true;
    };

    SQWORD GetScore(SQWORD sqNode) 
    {
        return score[sqNode];
    }
};


int main(void)
{
    SQWORD sqN = inputSQWORD();
    SQWORD sqM = inputSQWORD();
    SQWORD sqP = inputSQWORD();

    BellmanFordGraph graph(sqN + 1);

    for (SQWORD sqIdx = 0; sqIdx < sqM; sqIdx++) {
        SQWORD sqA = inputSQWORD();
        SQWORD sqB = inputSQWORD();
        SQWORD sqC = inputSQWORD();

        graph.AddEdge(sqA, sqB, sqC - sqP);
    }
    
    graph.searchUnpassableNode(1, sqN);
    if (graph.bellman_ford(1, sqN)) {
        printf("%lld\n", max((SQWORD)0, graph.GetScore(sqN)));
    } else {
        printf("-1\n");
    }

    return 0;
}

Measured memory_bytes: 768