#include <bits/stdc++.h>

using namespace std;

void fast_io() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
}
int main() {
    fast_io();
    int n, m;
    cin >> n >> m;
    vector<vector<pair<int, int>>> g(n);
    for (int i = 0; i < m; i++) {
        int u, v;
        string e;
        cin >> u >> e >> v;
        u--;
        v--;
        if (e.size() == 5) {
            g[u].push_back({v, 1});
            g[v].push_back({u, 1});
        } else {
            g[u].push_back({v, 0});
            g[v].push_back({u, 0});
        }
    }
    vector<int> color(n, -1);
    vector<bool> vis(n, false);
    vector<int> ans;
    for (int i = 0; i < n; i++) {
        if (vis[i]) {
            continue;
        }
        vis[i] = true;
        queue<int> q;
        q.push(i);
        color[i] = 0;
        vector<vector<int>> verts(2);
        verts[0].push_back(i);
        while (!q.empty()) {
            int u = q.front();
            q.pop();
            for (auto [v, e] : g[u]) {
                if (color[v] == -1) {
                    color[v] = color[u] ^ e;
                    vis[v] = true;
                    verts[color[v]].push_back(v);
                    q.push(v);
                } else if (color[v] != color[u] ^ e) {
                    cout << "No" << endl;
                    return 0;
                }
            }
        }
        if (verts[0].size() < verts[1].size()) {
            swap(verts[0], verts[1]);
        }
        for (auto v : verts[0]) {
            ans.push_back(v);
        }
    }
    if (ans.size() >= (n + 1) / 2) {
        cout << "Yes" << endl;
        cout << ans.size() << endl;
        sort(ans.begin(), ans.end());
        for (int i = 0; i < ans.size(); i++) {
            cout << ans[i] + 1 << " ";
        }
        cout << endl;
    } else {
        cout << "No" << endl;
    }
}