import heapq

def main():
    # アルゴリズム一覧を見る
    # 嘘解法ですか
    n, m = map(int, input().split())
    vec = list(map(int, input().split()))
    lst = []
    for _ in range(m):
        a, b, c = map(int, input().split())
        a -= 1
        b -= 1
        lst.append((a, b, c - vec[a]))
    lst.append((n - 1, n, -vec[n - 1]))
    dist = [float('inf')] * (n + 1)
    dist[0] = 0
    cnt = 0
    while cnt < n + 10:
        end = True
        for a, b, c in lst:
            if dist[a] != float('inf') and dist[a] + c < dist[b]:
                dist[b] = dist[a] + c
                end = False
        if end:
            break
        cnt += 1
    if cnt == n + 10:
        print("inf")
    else:
        print(-dist[n])

if __name__ == "__main__":
    main()