n,m=map(int,input().split())
a=list(map(int,input().split()))
e=[]
for i in range(m):
  x,y,z=map(int,input().split())
  x-=1
  y-=1
  e+=[(x,y,z-a[x])]
X=10**20
v=[X]*n
v[0]=0
for i in range(n):
  f=0
  for x,y,z in e:
    if v[y]>v[x]+z:
      v[y]=v[x]+z
      f=1
  if f==0:
    break
print("inf" if f else -v[n-1]+a[n-1])