N,M=map(int,input().split())
A=list(map(int, input().split()))
n=N
def bellman_ford(s):
    d = [float('inf')]*n # 各頂点への最小コスト
    d[s] = 0 # 自身への距離は0
    for i in range(n):
        update = False # 更新が行われたか
        for x, y, z in g:
            if d[y] > d[x] + z:
                d[y] = d[x] + z
                update = True
        if not update:
            break
        # 負閉路が存在
        if i == n - 1:
            return -1
    return d

 
g=[]
D=[[]for _ in range(N)];C=[]
for _ in range(M):
  x,y,z=map(int,input().split())
  x-=1;y-=1
  C.append((x,y,z))
  D[y].append(x)
  #g.append([x, y, -z])
  
from collections import deque
d=deque()
V=[-1]*N 
V[N-1]=1
d.append(N-1)
while d:
  now=d.popleft()
  for nex in D[now]:
    if V[nex]==-1:
      V[nex]=1
      d.append(nex)
      
for x,y,z in C:
  if V[x]+V[y]==2:
    g.append((x,y,-A[y]+z))
#print(g,D)
ans=bellman_ford(0)
#print(ans)
if ans==-1:
  print('inf')
else:
  print(A[0]-ans[-1])