#include <iostream>
#include <vector>
#include <iomanip>

using namespace std;

#define MAX 200000000

class edge {
public:
    int c, f, t;
    int u, v, n;
    edge(int c, int f, int t, int u, int v, int n) : c(c), f(f), t(t), u(u), v(v), n(n) {};
    int cf() { return c - f; };
    edge* e;
};

int n, m, k;
vector<int> dist;
vector<edge*> pred;
vector<vector<edge*>> cities;

void FordBellman() {
    dist = vector<int>(n, MAX);
    dist[0] = 0;
    pred = vector<edge*>(n, nullptr);

    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < cities.size(); j++) {
            for (int r = 0; r < cities[j].size(); r++) {
                edge* e = cities[j][r];
                if (e->cf() == 0)
                    continue;
                int u = e->u;
                int v = e->v;
                int time = e->cf() == 1 ? e->t : -e->t;
                if (dist[v] > dist[u] + time) {
                    dist[v] = dist[u] + time;
                    pred[v] = e;
                }
            }
        }
    }
}

int MaxFlow() {
    int time = 0;
    FordBellman();
    if (pred[n - 1] == nullptr) {
        return MAX;
    }

    for (int i = n - 1; i != 0; i = pred[i]->u) {
        int t = pred[i]->cf() == 1 ? pred[i]->t : -pred[i]->t;
        pred[i]->f += 1;
        pred[i]->e->f -= 1;
        time += t;
    }

    return time;
}

int main() {
    freopen("brides.in", "r", stdin);
    freopen("brides.out", "w", stdout);

    cin >> n >> m >> k;

    cities.resize(n, vector<edge*>());
    for (int i = 0; i < m; i++) {
        int u, v;
        int t;
        cin >> u >> v >> t;
        edge* e1 = new edge(1, 0, t, u - 1, v - 1, i + 1);
        edge* e2 = new edge(1, 0, t, v - 1, u - 1, i + 1);
        e1->e = e2;
        e2->e = e1;
        cities[u - 1].push_back(e1);
        cities[v - 1].push_back(e2);
    }

    int time = 0;
    for (int i = 0; i < k; i++) {
        int tmp = MaxFlow();
        if (tmp == MAX) {
            cout << -1;
            return 0;
        }
        time += tmp;
    }

    printf("%.7f\n", time / (double)k);
    vector<vector<int>> ans;
    for (int i = 0; i < k; i++) {
        ans.push_back(vector<int>());
        for (int j = 0; j != n - 1;) {
            for (int r = 0; r < cities[j].size(); r++) {
                edge* e = cities[j][r];
                if (e->cf() == 0) {
                    e->c = MAX;
                    j = e->v;
                    ans.back().push_back(e->n);
                    break;
                }
            }
        }
    }


    for (auto vec: ans) {
        cout << vec.size() << " ";
        for (auto elem: vec)
            cout << elem << " ";
        cout << endl;
    }

    return 0;
}