class Town:
    def __init__(self):
        self.T = None
        self.V = []
        self.M = float('inf')
        
N, M = map(int, input().split())
T = [Town() for _ in range(N)]
for _ in range(M):
    a, b, c = map(int, input().split())
    T[a-1].V.append((b-1, c))
    T[b-1].V.append((a-1, c))
for i, t in enumerate(list(map(int, input().split()))):
    T[i].T = t
    
q = [(0, 0, 0)]
while len(q) > 0:
    i, m, p = q.pop(0)
    t = T[i]
    p += t.T
    m += t.T
    for j, c in t.V:
        nt = T[j]
        if T[j].M > m+c/p:
            T[j].M = m+c/p
            q.append((j, m+c/p, p))
print(int(T[N-1].M))