N, M = map(int, input().split())
A = list(map(int, input().split()))
E = []
for _ in range(M):
    a, b, c = map(int, input().split())
    E.append((a - 1, b - 1, A[b - 1] - c))
INF = 1 << 63
cost = [-INF] * N
cost[0] = A[0]
for _ in range(N - 1):
    for frm, to, t in E:
        if cost[frm] == -INF: continue
        if cost[to] < cost[frm] + t:
            cost[to] = cost[frm] + t
update = [False] * N
for _ in range(N):
    for frm, to, t in E:
        if cost[frm] == -INF: continue
        if cost[to] < cost[frm] + t:
            update[to] = True
        if update[frm]:
            update[to] = True
for i in range(N):
    if update[i]:
        cost[i] = INF
if cost[N - 1] == INF:
    print("inf")
else:
    print(cost[N - 1])