import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
# O(EV)

    

g = []


n,m = map(int,input().split())
n *= 2
alist = list(map(int,input().split()))
edge = [[] for i in range(n//2)]
for i in range(m):
    a,b,c = map(int,input().split())
    edge[b-1].append(a-1)
    a -= 1
    b -= 1
    g.append((a*2+1,b*2,c))
for i in range(n//2):
    g.append((i*2,i*2+1,-alist[i]))
start = n//2-1
d = collections.deque()
dist = [10**18 for i in range(n//2)]
d.append(start)
dist[start] = 0
while d:
    now = d.popleft()
    for i in edge[now]:
        if dist[i] > dist[now] + 1:
            dist[i] = dist[now] + 1
            d.append(i)


d = [float('inf')]*n # 各頂点への最小コスト
d[0] = 0 # 自身への距離は0
for i in range(n):
    update = False # 更新が行われたか
    check = [False for rrfrf in range(n)]
    for x, y, z in g:
        if d[y] > d[x] + z:
            d[y] = d[x] + z
            update = True
            check[y] = True
    if not update:
        break
    if i == n-1:
        for j in range(n-1):
            if check[j] == True and dist[j] != 10**18:
                exit(print('inf'))

        


print(-d[-1])