def bellman_ford(G, s):
    inf = 10 ** 18
    N = len(G)
    dist = [inf] * N
    negative = [False] * N
    dist[s] = 0
    for _ in range(N - 1):
        for u in range(N):
            if dist[u] >= inf//2:
                continue
            for v, c in G[u]:
                if dist[v] > dist[u] + c:
                    dist[v] = dist[u] + c
                    
    for _ in range(N):
        for u in range(N):
            if dist[u] >= inf//2:
                continue
            for v, c in G[u]:
                if dist[v] > dist[u] + c:
                    negative[v] = True
                if negative[u]:
                    negative[v] = True
                    
    return dist, negative

N, M = map(int, input().split())
A = list(map(int, input().split()))
G = [[] for i in range(N)]
for i in range(M):
    a, b, c = map(int, input().split())
    a, b = a - 1 , b - 1
    G[a].append((b, c - A[a]))
    
d, f = bellman_ford(G, 0)
if f[-1]:
    print("inf")
else:
    print(-d[-1]+A[-1])