from collections import defaultdict,deque
N,M=map(int,input().split())
A=list(map(int,input().split()))
G=[[] for _ in range(N)]
cost=defaultdict(int)
for _ in range(M):
    a,b,c=map(int,input().split())
    a-=1;b-=1
    G[a].append(b)
    cost[(a,b)]=c
kouho=[]
loop=set()
Q=deque()
Q.append((0,[]))
while Q:
    d,r=Q.popleft()
    r.append(d)
    if d==N-1:
        kouho.append(r)
        continue
    s=set(r)
    for n in G[d]:
        if n in s:
            tmp=r[r.index(n):]+[n]
            sat=0
            for i in range(len(tmp)-1):
                sat+=A[tmp[i]]-cost[(tmp[i],tmp[i+1])]
            sat+=tmp[-1]
            if sat>0:
                loop|=set(tmp)
        else:
            Q.append((n,r[:]))
ans=0
for k in kouho:
    for i in k:
        if i in loop:
            print("inf")
            exit()
    sat=0
    for i in range(len(k)-1):
        sat+=A[k[i]]-cost[(k[i],k[i+1])]
    sat+=A[-1]
    ans=max(ans,sat)
print(ans)