from heapq import *
N, M = map(int, input().split())
A = list(map(int, input().split()))
g = []
for _ in range(M):
	a, b, c = map(int, input().split())
	a -= 1
	b -= 1
	g.append((a, b, c))

assert(N <= 5)

inf = 10 ** 20

dist = [-inf] * N
dist[0] = 0
for i in range(2 * N):
	for u, v, c in g:
		if dist[u] != -inf and dist[v] < dist[u] + A[v] - c:
			dist[v] = dist[u] + A[v] - c
now_dist = dist[:]
for i in range(2 * N):
	for u, v, c in g:
		if dist[u] != -inf and dist[v] < dist[u] + A[v] - c:
			dist[v] = dist[u] + A[v] - c

if now_dist[N - 1] < dist[N - 1]:
	exit(print("inf"))
print(dist[N - 1] + A[0])