class UnionFind:
    def __init__(self,n):
        self.n = n
        self.parent_size = [-1]*n
 
    def leader(self,a):
        if self.parent_size[a] < 0:
            return a
        self.parent_size[a] = self.leader(self.parent_size[a])
        return self.parent_size[a]
 
    def merge(self,a,b):
        x, y = self.leader(a), self.leader(b)
        if x == y:
            return 
        if abs(self.parent_size[x]) < abs(self.parent_size[y]):
            x, y = y, x
        self.parent_size[x] += self.parent_size[y]
        self.parent_size[y] = x
        return 
 
    def same(self,a,b):
        return self.leader(a) == self.leader(b)
 
    def size(self,a):
        return abs(self.parent_size[self.leader(a)])
 
    def groups(self):
        result = [[] for _ in range(self.n)]
        for i in range(self.n):
            result[self.leader(i)].append(i)
        return [r for r in result if r != []]

N, M = map(int, input().split())
edge = [list(map(int, input().split())) for _ in range(M)]

edge.sort(key=lambda x:x[2])

UF = UnionFind(N)
C = [0]*6
for u, v, c in edge:
    u, v = u-1, v-1
    c -= 1
    if not UF.same(u, v):
        UF.merge(u, v)
        C[c] += 1

def func(C):
    if C in memo:
        return memo[C]
    cnt = 0
    for i in range(6):
        if C[i] != 0: break
        cnt += 1
    pre = -1
    ans = 0
    for i in range(cnt, 6):
        if C[i] != 0: pre = i
        L = list(C)
        L[pre] -= 1
        NC = tuple(L)
        ans += ((6/(6-cnt))+func(NC))*(1/(6-cnt))
    memo[C] = ans
    return ans

memo = dict()
memo[(0, 0, 0, 0, 0, 0)] = 0
print(func(tuple(C)))