using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        var order = SList(m);
        var tree = new List<(int to, int xor)>[n];
        for (var i = 0; i < tree.Length; ++i) tree[i] = new List<(int to, int xor)>();
        foreach (var o in order)
        {
            var s = o.Split();
            var i = int.Parse(s[0]) - 1;
            var j = int.Parse(s[2]) - 1;
            var xor = s[1] == "<==>" ? 0 : 1;
            tree[i].Add((j, xor));
            tree[j].Add((i, xor));
        }
        var color = Enumerable.Repeat(-1, n).ToArray();
        for (var i = 0; i < n; ++i)
        {
            if (color[i] < 0)
            {
                var dic = new Dictionary<int, int>();
                dic[i] = 0;
                if (!DFS(i, tree, dic))
                {
                    WriteLine("No");
                    return;
                }
                var zeros = dic.Count(kv => kv.Value == 0);
                if (zeros < dic.Count() / 2)
                {
                    foreach (var kv in dic) color[kv.Key] = kv.Value ^ 1;
                }
                else
                {
                    foreach (var kv in dic) color[kv.Key] = kv.Value;
                }
            }
        }
        var list = new List<int>();
        for (var i = 0; i < n; ++i) if (color[i] == 0) list.Add(i + 1);
        WriteLine("Yes");
        WriteLine(list.Count);
        WriteLine(string.Join(" ", list));
    }
    static bool DFS(int cur, List<(int to, int xor)>[] tree, Dictionary<int, int> dic)
    {
        var color = dic[cur];
        foreach (var next in tree[cur])
        {
            if (dic.ContainsKey(next.to))
            {
                if (dic[next.to] != (color ^ next.xor)) return false;
            }
            else
            {
                dic[next.to] = color ^ next.xor;
                if (!DFS(next.to, tree, dic)) return false;
            }
        }
        return true;
    }
}