import typing
import sys
from collections import deque, defaultdict
input = lambda: sys.stdin.readline().strip()
inf = 10**18
mod = 998244353

def BellmanFord(N, s, Edges):
  dist = [inf for _ in range(N)]
  dist[s] = 0
  # N-1回緩める
  for _ in range(N-1):
    changed = False
    for v_from, v_to, c in Edges:
      if dist[v_from] == inf:
        continue
      if dist[v_from]+c < dist[v_to]:
        dist[v_to] = dist[v_from]+c
        changed = True
    if not changed:
      return dist

  for _ in range(N-1):
    changed = False
    for v_from, v_to, c in Edges:
      # 非連結の場合はあり得る
      if dist[v_from] == inf:
        continue
      # -inf + c が -inf以外の何よりも小さいようなinfの値を選択する
      if dist[v_from]+c < dist[v_to]:
        dist[v_to] = -inf
        changed = True
    if not changed:
      return dist

  return dist

def solve():
  N, M = map(int, input().split())
  A = list(map(int, input().split()))
  Edges = [] # (v_from, v_to, cost)
  for _ in range(M):
    a, b, c = map(int, input().split())
    # v_fromを攻略して移動し，v_toへと到達する時間
    Edges.append((a-1, b-1, c-A[a-1]))
  dist = BellmanFord(N, 0, Edges)
  if dist[-1] == -inf:
    print('inf')
    return 
  # Nを攻略する時間を足す
  print(-dist[-1]+A[-1])


def main():
  t = 1
  for _ in range(t):
    solve()
main()