//*
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//*/

#include <bits/stdc++.h>

// #include <atcoder/all>
// #include <atcoder/lazysegtree>

using namespace std;
// using namespace atcoder;

// #define _GLIBCXX_DEBUG

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                        \
    cerr << #v << ":";                                      \
    for (int iiiiiiii = 0; iiiiiiii < v.size(); iiiiiiii++) \
        cerr << " " << v[iiiiiiii];                         \
    cerr << endl;
#define DEBUG_MAT(v)                                \
    cerr << #v << endl;                             \
    for (int iv = 0; iv < v.size(); iv++) {         \
        for (int jv = 0; jv < v[iv].size(); jv++) { \
            cerr << v[iv][jv] << " ";               \
        }                                           \
        cerr << endl;                               \
    }
typedef long long ll;
// #define int ll

#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define vs vector<string>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
    return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template <class S, class T>
ostream &operator<<(ostream &os, pair<S, T> p) {
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (int)(n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
void YES(bool t = true) {
    cout << (t ? "YES" : "NO") << endl;
}
void Yes(bool t = true) { cout << (t ? "Yes" : "No") << endl; }
void yes(bool t = true) { cout << (t ? "yes" : "no") << endl; }
void NO(bool t = true) { cout << (t ? "NO" : "YES") << endl; }
void No(bool t = true) { cout << (t ? "No" : "Yes") << endl; }
void no(bool t = true) { cout << (t ? "no" : "yes") << endl; }
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const long double pi = 3.1415926535897932384626433832795028841971L;
int popcount(ll t) { return __builtin_popcountll(t); }
// int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
// int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
vi dx = {0, 0, -1, 1}, dy = {-1, 1, 0, 0};
vi dx2 = {1, 1, 0, -1, -1, -1, 0, 1}, dy2 = {0, 1, 1, 1, 0, -1, -1, -1};
struct Setup_io {
    Setup_io() {
        ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
        cout << fixed << setprecision(25);
    }
} setup_io;
// const ll MOD = 1000000007;
// const ll MOD = 998244353;
// #define mp make_pair
// #define endl '\n'

class UnionFind {
  private:
    vi par_;      // �e
    vi ran_;      // �؂̐[��
    vi num_;      // �v�f��
    vi edge_num_; // �v�f��
  public:
    int n;
    int g; // group��

    UnionFind(int _n) {
        n = _n;
        g = n;
        par_.resize(n);
        ran_.resize(n);
        num_.resize(n);
        edge_num_.resize(n);
        for (int i = 0; i < n; i++) {
            par_[i] = i;
            ran_[i] = 0;
            num_[i] = 1;
            edge_num_[i] = 0;
        }
    }

    // �؂̍������߂�
    int find(int x) {
        if (par_[x] == x) {
            return x;
        } else {
            return par_[x] = find(par_[x]);
        }
    }

    // x��y�̑�����W���𕹍�
    void unite(int x, int y) {
        x = find(x);
        y = find(y);
        int numsum = num_[x] + num_[y];
        int edge_numsum = edge_num_[x] + edge_num_[y];
        if (x == y) {
            edge_num_[x]++;
            return;
        }
        if (ran_[x] < ran_[y]) {
            par_[x] = y;
        } else {
            par_[y] = x;
            if (ran_[x] == ran_[y]) {
                ran_[x]++;
            }
        }
        num_[x] = num_[y] = numsum;
        edge_num_[x] = edge_num_[y] = edge_numsum + 1;
        g--;
    }

    // x��y�������W���ɑ����邩�ۂ�
    bool same(int x, int y) {
        return find(x) == find(y);
    }

    int num(int x) {
        return num_[find(x)];
    }

    int edge_num(int x) {
        return edge_num_[find(x)];
    }
};

signed main() {
    int n, m;
    cin >> n >> m;

    UnionFind uf(2 * n);
    rep(i, m) {
        int u, v;
        string s;
        cin >> u >> s >> v;
        u--;
        v--;

        if (s.size() == 4) {
            uf.unite(u, v);
            uf.unite(u + n, v + n);
        } else {
            uf.unite(u, v + n);
            uf.unite(u + n, v);
        }
    }

    rep(i, n) {
        if (uf.same(i, i + n)) {
            No();
            return 0;
        }
    }

    Yes();
    set<int> root;
    rep(i, 2 * n) {
        if (i != uf.find(i)) {
            continue;
        }
        root.insert(i);
    }

    map<int, int> mp;
    rep(i, n) {
        int r = uf.find(i);
        mp[r]++;
    }

    set<int> good_root;
    for (auto r : root) {
        int v;
        if (r < n) {
            v = r + n;
        } else {
            v = r - n;
        }

        if (mp[v] > mp[r]) {
            good_root.insert(v);
        } else if (mp[v] == mp[r]) {
            if (v > r) {
                good_root.insert(v);
            }
        }
    }

    vi ans;
    rep(i, n) {
        if (good_root.count(uf.find(i))) {
            ans.push_back(i);
        }
    }
    cout << ans.size() << endl;
    rep(i, ans.size()) {
        cout << ans[i] + 1 << " \n"[i == ans.size() - 1];
    }
}