from collections import deque

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

for i in range(M):
    edge[i][2] = A[edge[i][1]-1]-edge[i][2]

INF = float("inf")
dist = [-INF]*N
dist[0] = A[0]
for i in range(N):
    flag = False
    for j in range(M):
        a, b, c = edge[j]
        if dist[a-1]+c > dist[b-1]:
            dist[b-1] = dist[a-1]+c
            flag = True
    if not flag:
        print(dist[-1])
        break
else:
    d = dist[:]
    for i in range(M):
        a, b, c = edge[i]
        if d[a-1]+c > d[b-1]:
            d[b-1] = d[a-1]+c
    G = [[] for _ in range(N)]
    for i in range(M):
        a, b, c = edge[i]
        G[a-1].append(b-1)
    visited = [False]*N
    for i in range(N):
        if d[i] != dist[i] and not visited[i]:
            visited[i] = True
            que = deque()
            que.append(i)
            while que:
                n = que.popleft()
                if n == N-1:
                    exit(print("inf"))
                for v in G[n]:
                    if not visited[v]:
                        visited[v] = True
                        que.append(v)
    print(dist[-1])