#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
bool yneos(bool a,bool upp=0){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;}
template<class T> void vec_out(vector<T> &p,int ty=0){
    if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
    else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}
template<class T> bool inside(T l,T x,T r){return l<=x&&x<r;}

namespace po167{
    struct UF
    {
        using _F = int;
        int _n;
        std::vector<_F> wei;
        std::vector<int> q;
        int component;
        UF(int n):_n(n), wei(n), component(n), par(n){
            for (int i = 0; i < n; i++){
                wei[i] =1, par[i] = i;
            }
        }
        void intialize(){
            for (auto x : q){
                wei[root(x)] = 1;
                par[x] = x;
            }
            component = (int)par.size();
            q = {};
        }
        //根っこを返す
        int root(int a){
            assert(0 <= a && a < _n);
            if (a == par[a]) return a;
            return par[a] = root(par[a]);
        }
        //trueなら1,falseなら0
        int same(int a, int b){
            assert(0 <= a && a < _n);
            assert(0 <= b && b < _n);
            if(root(a) == root(b)) return 1;
            else return 0;
        }
        _F size(int a){
            return wei[root(a)];
        }
        //a,bが違う根っこの元なら結合する,結合したらtrueを返す
        bool unite(int a,int b){
            a = root(a), b = root(b);
            if (a == b) return false;
            if (wei[a] < wei[b]) std::swap(a, b);
            par[b] = a;
            q.push_back(b);
            wei[a] += wei[b];
            component--;
            return true;
        }
    private:
        std::vector<int> par;
    };
}
using po167::UF;



void solve();
// CYAN / FREDERIC
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    rep(i, 0, t) solve();
}

void solve(){
    int N, M;
    cin >> N >> M;
    struct edge {
        int to;
        int ei;
        ll cost;
    };
    vector<vector<edge>> G(N);
    UF T(N);
    vector<int> A(M), B(M), U(M);
    vector<ll> C(M);
    rep(i, 0, M){
        cin >> A[i] >> B[i] >> C[i];
        A[i]--, B[i]--;
        if (T.unite(A[i], B[i])){
            G[A[i]].push_back({B[i], i + 1, C[i]});
            G[B[i]].push_back({A[i], i + 1, -C[i]});
            U[i] = 1;
        }
    }
    vector<int> seen(N), depth(N);
    vector<edge> pare(N);
    vector<ll> dist(N);
    rep(i, 0, N) if (seen[i] == 0){
        vector<int> order = {i};
        seen[i] = 1;
        rep(rp, 0, order.size()){
            int a = order[rp];
            for (auto e : G[a]){
                if (chmax(seen[e.to], 1)){
                    depth[e.to] = depth[a] + 1;
                    dist[e.to] = dist[a] + e.cost;
                    order.push_back(e.to);
                }
                else{
                    pare[a] = e;
                }
            }
        }
    }
    rep(i, 0, M) if (U[i] == 0){
        ll tmp = dist[A[i]] + C[i] - dist[B[i]];
        if (tmp){
            if (tmp < 0) swap(A[i], B[i]);
            vector<int> ans1 = {i + 1}, ans2;
            while (A[i] != B[i]){
                if (depth[A[i]] < depth[B[i]]){
                    ans1.push_back(pare[B[i]].ei);
                    B[i] = pare[B[i]].to;
                }
                else{
                    ans2.push_back(pare[A[i]].ei);
                    A[i] = pare[A[i]].to;
                }
            }
            reverse(all(ans2));
            ans2.insert(ans2.end(), all(ans1));
            cout << ans2.size() << "\n";
            cout << A[i] + 1 << "\n";
            vec_out(ans2);
            return;
        }
    }
    cout << "-1\n";
}