N,M = map(int,input().split())
A = list(map(int,input().split()))
ABC = [tuple(map(int,input().split())) for _ in range(M)]

es = [[] for _ in range(N)]
rs = [[] for _ in range(N)]
for a,b,c in ABC:
    a,b = a-1,b-1
    es[a].append(b)
    rs[b].append(a)

stack = [0]
vis_go = set([0])
while stack:
    v = stack.pop()
    for to in es[v]:
        if to in vis_go: continue
        vis_go.add(to)
        stack.append(to)
stack = [N-1]
vis_bk = set([N-1])
while stack:
    v = stack.pop()
    for to in rs[v]:
        if to in vis_bk: continue
        vis_bk.add(to)
        stack.append(to)
use = vis_go & vis_bk


INF = 10**18
dist = [INF] * N
dist[0] = -A[0]
for i in range(len(use)):
    for a,b,c in ABC:
        a,b = a-1,b-1
        if a not in use: continue
        if b not in use: continue
        dd = c - A[b]
        if dist[b] > dist[a] + dd:
            dist[b] = dist[a] + dd
            if i==len(use)-1:
                exit(print('inf'))

print(-dist[-1])