import sys
input = sys.stdin.readline

N,M=map(int,input().split())
A=list(map(int,input().split()))

E=[[] for i in range(N)]
E_INV=[[] for i in range(N)]

for i in range(M):
    a,b,c=map(int,input().split())
    a-=1
    b-=1
    E[a].append((b,c))
    E_INV[b].append(a)

USE=[0]*N
USE[N-1]=1
Q=[N-1]

while Q:
    x=Q.pop()
    for to in E_INV[x]:
        if USE[to]==0:
            USE[to]=1
            Q.append(to)

DP=[-1<<60]*N
DP[0]=A[0]

for tests in range(N+10):
    flag=0
    for i in range(N):
        if USE[i]==0:
            continue
        for to,c in E[i]:
            if USE[to]==0:
                continue
            if DP[to]<DP[i]+A[to]-c:
                DP[to]=DP[i]+A[to]-c
                flag=1

if flag==1:
    print("inf")
else:
    print(DP[-1])