from collections import defaultdict
def dfs(node, parent, dist, lengths):
    for neighbor, weight in graph[node]:
        if neighbor != parent:
            lengths[neighbor] = dist + weight
            dfs(neighbor, node, lengths[neighbor], lengths)
W, E = map(int, input().split())
w_stations = [i for i in range(1, W+1)]
e_stations = [i for i in range(W+1, W+E+1)]
graph = defaultdict(list)
for _ in range(W+E-1):
    u, v, w = map(int, input().split())
    graph[u].append((v, w))
    graph[v].append((u, w))
w_lengths = defaultdict(int)
e_lengths = defaultdict(int)
for node in w_stations:
    dfs(node, 0, 0, w_lengths)
for node in e_stations:
    dfs(node, 0, 0, e_lengths)
options = []
for w_node in w_stations:
    for e_node in e_stations:
        length = w_lengths[w_node] + e_lengths[e_node]
        for node in w_stations:
            if node != w_node:
                length += w_lengths[node]
        for node in e_stations:
            if node != e_node:
                length += e_lengths[node]
        options.append(length / (W+E-1))