# 標準入力された値を整数に変換する
def INT():
    return int(input())


# 標準入力された複数の値を整数に変換する
def MI():
    return map(int, input().split())


# 標準入力された複数の値を整数のリストに変換する
def LI():
    return list(map(int, input().split()))


class UnionFind:
    def __init__(self, N):
        self.root = [_ for _ in range(N)]
        self.rank = [0] * N
        self.size = [1] * N

    def find(self, x):
        if self.root[x] == x:
            return x
        else:
            # 根を予め取得し,経路圧縮する
            self.root[x] = self.find(self.root[x])
            return self.root[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return
        else:
            if self.rank[x] > self.rank[y]:
                self.size[x] += self.size[y]
                self.root[y] = x
            else:
                self.size[y] += self.size[x]
                self.root[x] = y
                if self.rank[x] == self.rank[y]:
                    self.rank[y] += 1

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def getSizeOfSet(self, x):
        return self.size[self.find(x)]


import heapq


def dijkstra(n, G, start=0):
    INF = 10**18
    dist = [INF] * n
    dist[start] = 0
    pq = []
    heapq.heappush(pq, (0, start))
    visited = [False] * n

    while pq:
        now = heapq.heappop(pq)[1]
        visited[now] = True
        for nxt, cost in G[now]:
            if dist[nxt] > dist[now] + cost and not visited[nxt]:
                dist[nxt] = dist[now] + cost
                heapq.heappush(pq, (dist[now] + cost, nxt))

    return dist


N, M = MI()
A = LI()
G = [[] for i in range(N)]
dsu = UnionFind(N)
for _ in range(M):
    a, b, c = MI()
    a -= 1
    b -= 1
    G[a].append((b, A[b] - c))
    if dsu.same(a, b):
        print("inf")
        exit(0)
    dsu.union(a, b)

dist = dijkstra(N, G)
print(dist[-1] + A[0])