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))

inf = 10 ** 18

dist = [-inf] * N
dist[0] = 0
for i in range(N - 1):
	for u, v, c in g:
		if dist[u] != -inf and dist[v] < dist[u] + A[u] - c:
			dist[v] = dist[u] + A[u] - c
for u, v, c in g:
	if dist[v] < dist[u] + A[u] - c:
		exit(print("inf"))
print(dist[N - 1] + A[N - 1] if dist[N - 1] > -inf else "inf")