import heapq

def solve(n, m, a, uvw):
  graph = [[] for _ in range(n)]
  for ui, vi, wi in uvw:
    graph[ui-1].append((vi - 1, wi))

  pq = [(-a[0], 0)]
  mn = [10 ** 18] * n
  mn[0] = -a[0]
  while True:
    cost, node = heapq.heappop(pq)
    if node == n - 1:
      return -cost
    if mn[node] < cost:
      continue
    if cost < mn[node]:
      return "inf"
    for next_node, next_cost in graph[node]:
      if a[next_node] <= -cost - next_cost:
        continue
      a[next_node] = -cost + next_cost
      heapq.heappush(pq, (-a[next_node], next_node))

n, m = [int(x) for x in input().split()]
a = [int(x) for x in input().split()]
uvw = [[int(x) for x in input().split()] for _ in range(m)]

print(solve(n, m, a, uvw))