N, M = map(int, input().split())
A = list(map(int, input().split()))

G = [[] for _ in range(N)]
Grev = [[] for _ in range(N)]
E = []
for i in range(M):
    a, b, c = map(int, input().split())
    a -= 1
    b -= 1
    G[a].append(b)
    c *= -1
    c += A[b]
    E.append((a, b, c))
    Grev[b].append(a)

def BF(start):
    # Bellman-Ford
    score = [-float('inf')] * N # スタート地点からの最小距離
    score[start] = A[start]

    for i in range(N):
        update = False # 更新が行われたか
        for u, v, weight in E:
            if score[v] < score[u] + weight:
                score[v] = score[u] + weight
                update = True
        if not update:
            break
        # 負閉路が存在するときは負閉路内の頂点リストを返す
        if i == N - 1:
            st = set()
            for u, v, weight in E:
                if score[v] < score[u] + weight:
                    score[v] = score[u] + weight
                    st.add(v)
            return 1, score, st
    return 0, score, 0

from collections import deque
# print(E)
state, score, st = BF(0) # ノード0から各地点の最短距離
if state == 0:
    print(score[N-1])
else:
    sctmp = score[N-1]
    goal = st
    que = deque()
    visited = [False]*N
    stt = N-1
    visited[stt] = True
    que.append(stt)
    # print(goal)
    while que:
        now = que.popleft()
        for to in Grev[now]:
            if visited[to] == False:
                if to in goal:
                    print('inf')
                    exit()
                visited[to] = True
                que.append(to)
    print(sctmp)