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

INF = 10**18
dist = [INF] * N
dist[0] = -A[0]
for i in range(N):
    for a,b,c in ABC:
        a,b = a-1,b-1
        dd = c - A[b]
        if dist[b] > dist[a] + dd:
            dist[b] = dist[a] + dd
            if i==N-1:
                exit(print('inf'))

print(-dist[-1])