#include <bits/stdc++.h>
#define rep(i, n) for(long long i = 0; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
using namespace std;

using lint = long long;

template <class T = long long>
struct WeightedUnionFind {
    private:
    int n;
    vector<int> par;
    vector<T> diff_weight;
    
    public:
    WeightedUnionFind() {}
    WeightedUnionFind(int n_) : n(n_), par(n, -1), diff_weight(n, T(0)) {}
    
    int leader(int x) {
        assert(0 <= x && x < n);
        if (par[x] < 0) {
            return x;
        } else {
            int r = leader(par[x]);
            diff_weight[x] += diff_weight[par[x]];
            return par[x] = r;
        }
    }
    
    T weight(int x) {
        assert(0 <= x && x < n);
        leader(x);
        return diff_weight[x];
    }
    
    T diff(int x, int y) {
        assert(0 <= x && x < n);
        assert(0 <= y && y < n);
        return weight(y) - weight(x);
    }
    
    int merge(int x, int y, T w) {
        assert(0 <= x && x < n);
        assert(0 <= y && y < n);
        w += weight(x);
        w -= weight(y);
        x = leader(x);
        y = leader(y);
        if (x == y) {
            return x;
        }
        if (-par[x] < -par[y]) {
            swap(x, y);
            w *= T(-1);
        }
        par[x] += par[y];
        par[y] = x;
        diff_weight[y] = w;
        return x;
    }
    
    bool same(int x, int y) {
        assert(0 <= x && x < n);
        assert(0 <= y && y < n);
        return leader(x) == leader(y);
    }
    
    int size(int x) {
        assert(0 <= x && x < n);
        return -par[leader(x)];
    }
    
    vector<vector<int>> groups() {
        vector<vector<int>> member(n);
        for (int i = 0; i < n; i++) {
            member[leader(i)].emplace_back(i);
        }
        vector<vector<int>> res;
        for (int i = 0; i < n; i++) {
            if (member[i].size() > 0) {
                res.emplace_back(member[i]);
            }
        }
        return res;
    }
};

template <class T>
struct Edge {
    int from, to;
    T cost;
    int idx;
    
    Edge() {}
    Edge(int to_) : to(to_) {}
    Edge(int to_, T cost_) : to(to_), cost(cost_) {}
    Edge(int from_, int to_, int idx_) : from(from_), to(to_), idx(idx_) {}
    Edge(int from_, int to_, T cost_, int idx_) : from(from_), to(to_), cost(cost_), idx(idx_) {}
};

template <class T> using Graph = vector<vector<Edge<T>>>;
using graph = Graph<long long>;
using edge = Edge<long long>;

#define add emplace_back

struct Dijkstra {
    private:
    graph g;
    int n, s;
    vector<long long> d;
    vector<edge> prev;
    vector<bool> visit;
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq;
    
    public:
    Dijkstra(graph g_, int s_) : g(g_), n(g.size()), s(s_), d(n, 1000000000000000000), prev(n), visit(n, false) {
        d[s] = 0LL;
        pq.emplace(d[s], s);
        while (!pq.empty()) {
            int v = pq.top().second;
            pq.pop();
            if (visit[v]) {
                continue;
            }
            visit[v] = true;
            for (auto e : g[v]) {
                int nv = e.to;
                long long nc = e.cost;
                if (d[nv] > d[v] + nc) {
                    d[nv] = d[v] + nc;
                    prev[nv] = e;
                    pq.emplace(d[nv], nv);
                }
            }
        }
    }
    
    vector<long long> dists() {
        return d;
    }
    
    long long dist(int t) {
        return d[t];
    }
    
    vector<edge> route(int t) {
        if (s == t || d[t] == 1000000000000000000) {
            return {};
        }
        vector<edge> res;
        int cur = t;
        while (cur != s) {
            res.emplace_back(prev[cur]);
            cur = prev[cur].from;
        }
        reverse(res.begin(), res.end());
        return res;
    }
};

int main() {
    int n, m;
    cin >> n >> m;
    WeightedUnionFind uf(n);
    graph g(n);
    int s = -1, t = -1, id = -1;
    rep(i, m) {
        int u, v;
        lint w;
        cin >> u >> v >> w;
        u--;
        v--;
        if (!uf.same(u, v)) {
            uf.merge(v, u, w);
            g[u].add(u, v, w, i);
            g[v].add(v, u, w, i);
        } else {
            lint d = uf.diff(v, u);
            if (d == w) {
                uf.merge(v, u, w);
                g[u].add(u, v, w, i);
                g[v].add(v, u, w, i);
            } else if (d > w) {
                s = u;
                t = v;
                id = i;
                break;
            } else {
                s = v;
                t = u;
                id = i;
                break;
            }
        }
    }
    if (s >= 0) {
        auto r = Dijkstra(g, s).route(t);
        cout << r.size() + 1 << endl << s + 1 << endl;
        for (auto e : r) {
            cout << e.idx + 1 << " ";
        }
        cout << id + 1 << endl;
        return 0;
    }
    cout << -1 << endl;
}