Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-
import sys
# sys.setrecursionlimit(10**6)
# buff_readline = sys.stdin.buffer.readline
buff_readline = sys.stdin.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(buff_readline())


def read_int_n():
    return list(map(int, buff_readline().split()))


def read_float():
    return float(buff_readline())


def read_float_n():
    return list(map(float, buff_readline().split()))


def read_str():
    return readline().strip()


def read_str_n():
    return readline().strip().split()


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


from collections import defaultdict

def BellmanFord(g, s, N):
    dist = [INF] * (N+1)
    dist[s] = 0
    for i in range(N):
        for u in range(1, N+1):
            if dist[u] == INF:
                continue
            for v in g[u]:
                if dist[v] > dist[u] + g[u][v]:
                    dist[v] = dist[u] + g[u][v]
    for i in range(N):
        for u in range(1, N+1):
            if dist[u] == INF:
                continue
            for v in g[u]:
                if dist[v] > dist[u] + g[u][v]:
                    if dist[v] != INF:
                        dist[v] = -INF
    return dist


@mt
def slv(N, M, P, ABC):
    g = defaultdict(dict)
    for a, b, c in ABC:
        if a in g and b in g[a]:
            g[a][b] = min(g[a][b], -(c - P))
        else:
            g[a][b] = -(c - P)

    d = BellmanFord(g, 1, N)
    if -d[N] >= INF:
        return -1
    return max(0, -d[N])





def main():
    N, M, P = read_int_n()
    ABC = [read_int_n() for _ in range(M)]
    print(slv(N, M, P, ABC))


if __name__ == '__main__':
    main()


Fixed submission:
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)
input = sys.stdin.readline


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


def BellmanFord(N, e, s, goal):

    dist = defaultdict(lambda: sys.maxsize)
    pred = defaultdict(lambda: -1)

    dist = [sys.maxsize] * (N+1)
    dist[s] = 0
    for _ in range(N+1):
        for u, v, c in e:
            if dist[v] > dist[u] + c:
                dist[v] = dist[u] + c
    
    d = dist[goal]
    for _ in range(N+1):
        for u, v, c in e:
            if dist[v] > dist[u] + c:
                dist[v] = dist[u] + c
    return dist, d != dist[goal]

@mt
def slv(N, M, P, ABC):

    e = []
    for a, b, c in ABC:
        e.append((a, b, -(c - P)))

    d, loop = BellmanFord(N, e, 1, N)
    return max(0, -d[N]) if not loop else -1


def main():
    N, M, P = read_int_n()
    ABC = [read_int_n() for _ in range(M)]
    print(slv(N, M, P, ABC))

    # N = 2500
    # M = 5000
    # P = random.randint(0, 10**5)
    # P= 0
    # ABC = [
    #     [random.randint(1, N), random.randint(1, N), random.randint(1, 10**5)] for _ in range(M)
    # ]
    # print(slv(N, M, P, ABC))



if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)
input = sys.stdin.readline


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


def BellmanFord(g, s):
    V = list(g.keys())
    for v in g.values():
        V.extend(list(v.keys()))
    V = set(V)

    dist = defaultdict(lambda: sys.maxsize)
    pred = defaultdict(lambda: -1)

    dist[s] = 0

    N = len(V)
    for i in range(N+1):
        for u in g:
            for v in g[u]:
                if dist[v] > dist[u] + g[u][v]:
                    if i == N:
                        return 'inf'
                    dist[v] = dist[u] + g[u][v]
                    pred[v] = u
    return dist


@mt
def slv(N, M, P, ABC):

    g =defaultdict(dict)
    for a, b, c in ABC:
        g[a][b] = -(c - P)

    def r(s):
        q = [s]
        done = set()
        done.add(s)
        while q:
            v = q.pop()
            for u in g[v]:
                done.add(u)
        return N in done, done
    
    _, r1 = r(1)
    for i in range(2, N):
        if i not in r1:
            g.pop(i)

    d = set()
    for i in range(2, N):
        a, _ = r(i)
        d.add(i)
    
    for i in d:
        g.pop(i)
    for k, v in g.items():
        for i in d:
            if i in v:
                v.pop(i)

    d = BellmanFord(g, 1)
    if d == 'inf':
        return -1
    return max(0, -d[N])


def main():
    N, M, P = read_int_n()
    ABC = [read_int_n() for _ in range(M)]
    print(slv(N, M, P, ABC))


if __name__ == '__main__':
    main()


Fixed submission:
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)
input = sys.stdin.readline


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


def BellmanFord(N, e, s, goal):

    dist = defaultdict(lambda: sys.maxsize)
    pred = defaultdict(lambda: -1)

    dist = [sys.maxsize] * (N+1)
    dist[s] = 0
    for _ in range(N+1):
        for u, v, c in e:
            if dist[v] > dist[u] + c:
                dist[v] = dist[u] + c
    
    d = dist[goal]
    for _ in range(N+1):
        for u, v, c in e:
            if dist[v] > dist[u] + c:
                dist[v] = dist[u] + c
    return dist, d != dist[goal]

@mt
def slv(N, M, P, ABC):

    e = []
    for a, b, c in ABC:
        e.append((a, b, -(c - P)))

    d, loop = BellmanFord(N, e, 1, N)
    return max(0, -d[N]) if not loop else -1


def main():
    N, M, P = read_int_n()
    ABC = [read_int_n() for _ in range(M)]
    print(slv(N, M, P, ABC))

    # N = 2500
    # M = 5000
    # P = random.randint(0, 10**5)
    # P= 0
    # ABC = [
    #     [random.randint(1, N), random.randint(1, N), random.randint(1, 10**5)] for _ in range(M)
    # ]
    # print(slv(N, M, P, ABC))



if __name__ == '__main__':
    main()