from heapq import *
N, M = map(int, input().split())
A = list(map(int, input().split()))
g = [[] for _ in range(N)]
for _ in range(M):
	a, b, c = map(int, input().split())
	a -= 1
	b -= 1
	g[a].append((b, c))
d = [-10 ** 18] * N
d[0] = A[0]
q = [(-A[0], 0)]
while q:
	di, u = heappop(q)
	di = -di
	if di < d[u]:
		continue
	for v, c in g[u]:
		if di + A[v] - c > d[v] > -10 ** 18:
			exit(print("inf"))
		if di + A[v] - c > d[v]:
			d[v] = di + A[v] - c
			heappush(q, (-d[v], v))
print(d[N - 1])