# oj t -c "python3 main.py"
import sys,math
from collections import defaultdict,deque
from itertools import combinations,permutations,accumulate,product
from bisect import bisect,bisect_left,bisect_right
from heapq import heappop,heappush,heapify
#from sortedcontainers import SortedList,SortedSet
def input(): return sys.stdin.readline().rstrip()
def ii(): return int(input())
def ms(): return map(int, input().split())
def li(): return list(map(int,input().split()))
inf = pow(10,18)
#////////////////////////////////////
N,M = ms()
A = [-1]+li()
G = [set() for _ in range(N+1)]
for _ in range(M):
  u,v,c = ms()
  G[u].add((v,c))
H = []
heappush(H,(-A[1],1))
visited = [False]*(N+1)
while H:
  c,v = heappop(H)
  if visited[v]: continue
  c *= -1
  if v==N: 
    print(c)
    exit()
  visited[v] = True
  for v2,c2 in G[v]:
    if A[v2]<c2: continue
    if A[v2]>c2 and visited[v2]:
      print('inf')
      exit()
    if visited[v2] and A[v2]!=c2: continue
    heappush(H,(-(c+A[v2]-c2),v2))