#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


struct union_find{
    vector<int> par;
    vector<int> siz;
    
    union_find(int n) : par(n), siz(n, 1){
        for(int i=0; i<n; i++) par[i] = i;
    }
    
    int root(int x){
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }
 
    void unite(int x, int y){
        int rx = root(x);
        int ry = root(y);
        if (rx == ry) return;
        if (siz[rx] < siz[ry]) swap(rx, ry);
        siz[rx] += siz[ry];
        par[ry] = rx;
    }
 
    bool same(int x, int y){
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }
 
    int size(int x){
        return siz[root(x)];
    }
};

using ld = long double;

void solve(){
    int n, m; cin >> n >> m;
    vector<tuple<int, int, int>> es(m);
    for (int i = 0; i < m; i++) {
        int a, b, c; cin >> a >> b >> c;
        a--; b--; c--;
        es[i] = {c, a, b};
    }
    sort(all(es));
    union_find uf(n);
    vector<int> init_cnt(6, 0);
    for(int i=0; i<m; i++){
        auto [c, a, b] = es[i];
        if(uf.same(a, b)) continue;
        uf.unite(a, b);
        init_cnt[c]++;
    }

    map<vector<int>, ld> dp;
    dp[{0, 0, 0, 0, 0, 0}] = 0;
    function<void(vector<int>)> dfs = [&](vector<int> cnt){
        if(dp.find(cnt) != dp.end()) return;
        vector<int> pre(6, 0);
        pre[0] = -1;
        if(cnt[0] > 0) pre[0] = 0;
        for(int i=1; i<6; i++){
            pre[i] = pre[i-1];
            if(cnt[i] > 0) pre[i] = i;
        }
        int c = 0;
        dp[cnt] = 1;
        for(int i=0; i<6; i++){
            if(pre[i] == -1){
                c++;
            }else{
                vector<int> nxt = cnt;
                nxt[pre[i]]--;
                dfs(nxt);
                dp[cnt] += dp[nxt]/(ld)6;
                nxt[pre[i]]++;
            }
        }
        dp[cnt] /= (1 - (ld)c/(ld)6);
    }; dfs(init_cnt);

    cout << fixed << setprecision(10) << dp[init_cnt] << '\n';
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}