#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint998244353;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

// ポテンシャル付 Union-Find
// https://qiita.com/drken/items/cce6fc5c579051e64fab#%E9%87%8D%E3%81%BF%E3%81%A4%E3%81%8D-unionfind-%E6%9C%A8%E3%81%AE%E5%87%A6%E7%90%86
struct UnionFind {
    vector<int> par;
    vector<int> rank;
    vector<ll> diff_weight;

    UnionFind(int n = 1, ll SUM_UNITY = 0) { init(n, SUM_UNITY); }

    void init(int n = 1, ll SUM_UNITY = 0) {
        par.resize(n);
        rank.resize(n);
        diff_weight.resize(n);
        for (int i = 0; i < n; ++i)
            par[i] = i, rank[i] = 0, diff_weight[i] = SUM_UNITY;
    }

    int root(int x) {
        if (par[x] == x) {
            return x;
        } else {
            int r = root(par[x]);
            diff_weight[x] += diff_weight[par[x]];
            return par[x] = r;
        }
    }

    ll weight(int x) {
        root(x);
        return diff_weight[x];
    }

    bool issame(int x, int y) { return root(x) == root(y); }

    bool merge(int x, int y, ll w) {
        w += weight(x);
        w -= weight(y);
        x = root(x);
        y = root(y);
        if (x == y) return false;
        if (rank[x] < rank[y]) swap(x, y), w = -w;
        if (rank[x] == rank[y]) ++rank[x];
        par[y] = x;
        diff_weight[y] = w;
        return true;
    }

    ll diff(int x, int y) { return weight(y) - weight(x); }
};

ll INF = 1000000000023LL;

vector<ll> find_route(vector<vector<pll>> &graph, ll start, ll goal){
    queue<ll> que;
    que.push(start);
    ll N = graph.size();
    vector<ll> dist(N, INF);
    dist[start] = 0;
    while (que.size()){
        ll p = que.front();
        que.pop();
        for (pll x: graph[p]){
            if (dist[x.first] < INF) continue;
            dist[x.first] = dist[p] + 1;
        }
    }

    vector<ll> vec;
    ll now = goal;
    while (true){
        if (now == start) break;
        for (pll x: graph[now]){
            if (dist[x.first] < dist[now]){
                vec.push_back(x.second);
                now = x.first;
            }
        }
    }
    reverse(all(vec));
    return vec;
}

int main() {
    ll N, M;
    cin >> N >> M;
    vector<ll> u(M);
    vector<ll> v(M);
    vector<ll> w(M);
    for (ll i = 0; i < M; i++){
        cin >> u[i] >> v[i] >> w[i];
        u[i]--;
        v[i]--;
    }
    UnionFind tree(N);
    vector<vector<pll>> graph(N, vector<pll>(0));
    for (ll i = 0; i < M; i++){
        if (!tree.issame(u[i], v[i])){
            tree.merge(u[i], v[i], w[i]);
            graph[u[i]].push_back(make_pair(v[i], i));
            graph[v[i]].push_back(make_pair(u[i], i));
        }
        else if (tree.diff(u[i], v[i]) == w[i]){
            continue;
        }
        else if (tree.diff(u[i], v[i]) < w[i]){
            vector<ll> route = find_route(graph, v[i], u[i]);
            route.push_back(i);
            ll L = route.size();
            cout << L << endl;
            cout << v[i] + 1 << endl;
            for (ll i = 0; i < L; i++){
                cout << route[i] + 1;
                if (i < L - 1) cout << " ";
            }
            cout << endl;
            return 0;
        }
        else{
            vector<ll> route = find_route(graph, u[i], v[i]);
            route.push_back(i);
            ll L = route.size();
            cout << L << endl;
            cout << u[i] + 1 << endl;
            for (ll i = 0; i < L; i++){
                cout << route[i] + 1;
                if (i < L - 1) cout << " ";
            }
            cout << endl;
            return 0;
        }
    }
    cout << -1 << endl;
}