N,M = map(int,input().split())
A = list(map(int,input().split()))
INF = float('inf')
cost = [[-INF] * N for _ in range(N)]
for i in range(N):
    cost[i][i] = 0
for _ in range(M):
    a,b,c = map(int,input().split())
    a -= 1
    b -= 1
    cost[a][b] = A[b] - c

# cost[i][j]: 頂点v_iから頂点v_jへ到達するための辺コストの和
for k in range(N):
    for i in range(N):
        for j in range(N):
            if cost[i][k]!=-INF and cost[k][j]!=-INF:
                cost[i][j] = max(cost[i][j], cost[i][k] + cost[k][j])

for i in range(N):
    if cost[i][i] > 0 and cost[i][-1] != -INF:
        print("inf")
        exit()
print(A[0]+cost[0][-1])