namespace AtCoder;

#nullable enable

using System.Numerics;

static class Extensions
{
    public static T[] Repeat<T>(this int time, Func<T> F) => Enumerable.Range(0, time).Select(_ => F()).ToArray();
}

class AtCoder
{
    object? Solve()
    {
        var n = Int();
        var m = Int();
        var adjz = n.Repeat(() => new Dictionary<int, (int, int)>());
        for (var i = 0; i < m; i++)
        {
            var u = Int() - 1;
            var v = Int() - 1;
            var w = Int();
            if (adjz[u].TryGetValue(v, out var p))
            {
                var (pw, pj) = p;
                if (pw == w) continue;
                Out(2);
                if (w > pw)
                {
                    Out(v + 1);
                }
                else
                {
                    Out(u + 1);
                }
                Out(pj + " " + (i + 1));
                return null;
            }
            adjz[u][v] = (w, i + 1);
            adjz[v][u] = (-w, i + 1);
        }
        var dz = new long[n];
        var last = n.Repeat(() => -1);
        var lj = n.Repeat(() => -1);
        var ans = new List<int>();
        void S(int v, int prev)
        {
            if (ans.Count > 0) return;
            foreach (var (next, value) in adjz[v])
            {
                var (w, j) = value;
                if (j == prev) continue;
                var nd = dz[v] + w;
                if (last[next] != -1)
                {
                    if (dz[next] != nd && ans.Count == 0)
                    {
                        var k = v;
                        ans.Add(j);
                        while (k != next && k >= 0)
                        {
                            ans.Add(lj[k]);
                            k = last[k];
                        }
                        if (dz[next] < nd) ans.Reverse();
                        Out(ans.Count);
                        Out(next + 1);
                        Out(ans, " ");
                        return;
                    }
                    continue;
                }
                dz[next] = nd;
                last[next] = v;
                lj[next] = j;
                S(next, j);
            }
        }
        for (var start = 0; start < n; start++)
        {
            if (last[start] != -1) continue;
            dz[start] = 0;
            last[start] = -2;
            S(start, -1);
        }
        if (ans.Count == 0) return -1;
        return null;
    }

    public static void Main() => new AtCoder().Run();
    public void Run()
    {
        var res = Solve();
        if (res != null)
        {
            if (res is bool yes) res = yes ? "Yes" : "No";
            sw.WriteLine(res);
        }
        sw.Flush();
    }

    string[] input = Array.Empty<string>();
    int iter = 0;
    readonly StreamWriter sw = new(Console.OpenStandardOutput()) { AutoFlush = false };

    string String()
    {
        while (iter >= input.Length) (input, iter) = (Console.ReadLine()!.Trim().Split(' '), 0);
        return input[iter++];
    }
    T Input<T>() where T : IParsable<T> => T.Parse(String(), null);
    int Int() => Input<int>();
    void Out(object? x, string? separator = null)
    {
        separator ??= Environment.NewLine;
        if (x is System.Collections.IEnumerable obj and not string)
        {
            var firstLine = true;
            foreach (var item in obj)
            {
                if (!firstLine) sw.Write(separator);
                firstLine = false;
                sw.Write(item);
            }
        }
        else sw.Write(x);
        sw.WriteLine();
    }
}