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
      p=y
if f==0:
  print(-v[-1]+a[-1])
else:
  E=[[] for i in range(n)]
  for x,y,z in e:
    E[x]+=[y]
  q=[p]
  u=[0]*n
  u[p]=1
  for s in q:
    for t in E[s]:
      if u[t]==0:
        u[t]=1
        q+=[t]
  print(-v[-1]+a[-1] if u[-1]==0 else "inf")