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 - A[b]))

d = [10 ** 100]*N
d[0] = 0
for i in range(N):
    update = False
    for x, y, z in g:
        if d[y] > d[x] + z:
            d[y] = d[x] + z
            update = True
    if not update:
        break
    if i == N - 1:
        exit(print("inf"))
print(A[0] - d[N - 1])