#include <bits/stdc++.h>
using namespace std;

#define int long long

#define rep(i, a, b) for (auto i = a; i < (b); ++i)
#define repr(i, a, b) for (auto i = (a) - 1; i >= (b); --i)
#define pb push_back
#define eb emplace_back
#define all(x) begin(x), end(x)
#define sz(x) (int)((x).size())
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vii = vector<pii>;

template<class T>
inline bool cmax(T &a, const T& b) {
    return a < b ? a = b, 1 : 0;
    return b < a ? a = b, 1 : 0;
}

const int inf = 0x3f3f3f3f;
const ll linf = 1e18;
const double dinf = numeric_limits<double>::infinity();

pair<int, vi> hungarian(const vector<vi> &a) {
    if (a.empty())
        return {0, {}};
    int n = sz(a) + 1, m = sz(a[0]) + 1;
    vi u(n), v(m), p(m), ans(n - 1);
    rep(i, 1, n) {
        p[0] = i;
        int j0 = 0;
        vi dist(m, INT_MAX), pre(m, -1);
        vector<bool> done(m + 1);
        do {
            done[j0]= true;
            int i0 = p[j0], j1, delta = INT_MAX;
            rep(j, 1, m) if (!done[j]) {
                auto cur = a[i0 - 1][j - 1] - u[i0] - v[j];
                if (cur < dist[j])
                    dist[j] = cur, pre[j] = j0;
                if (dist[j] < delta)
                    delta = dist[j], j1 = j;
            }
            rep(j, 0, m) {
                if (done[j])
                    u[p[j]] += delta, v[j] -= delta;
                else
                    dist[j] -= delta;
            }
            j0 = j1;
        } while (p[j0]);
        while (j0) {
            int j1 = pre[j0];
            p[j0] = p[j1], j0 = j1;
        }
    } 
    rep(j, 1, m) 
        if (p[j])
            ans[p[j] - 1] = j - 1;
    return {-v[0], ans};
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int n, m;
    cin >> n >> m;
    vector<vi> cost(n, vi(n, inf));
    rep(i, 0, n) {
        cost[i][i] = 0;
    }
    rep(i, 0, m) {
        int f, h, a;
        cin >> f >> h >> a;
        --f;
        --h;
        cost[f][h] = -a;
    }    

    auto [ans, match] = hungarian(cost);
    ans = -ans;
    // int ans = -hungarian(cost).first;

    
    cout << fixed << setprecision(10) << double(ans) / 20.0 << '\n';
    // rep(i, 0, n) {
    //     cerr << match[i] << ' ';
    // }
    // cerr << endl;

    return 0;
}