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

G = [[] 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))

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-1を返す
        if i == N - 1:
            check = score[N-1]
            for u, v, weight in E:
                if score[v] < score[u] + weight:
                    score[v] = score[u] + weight
                    update = True
            check2 = score[N-1]
            if check == check2:
                print(check)
                exit()
            else:
                return -1
    return score
# print(E)
score = BF(0) # ノード0から各地点の最短距離
if score == -1:
    print('inf')
else:
    print(score[N-1])