#include <bits/stdc++.h>

using namespace std;
using ll = long long;

struct UnionFind {
    int ngroup, N;
    vector<int> par, siz, mn;

    UnionFind(int _N) : N(_N), par(_N), siz(_N), mn(_N) {
        ngroup = _N;
        for(int i = 0; i < N; i++) par[i] = i, siz[i] = 1, mn[i] = i;
    }

    int root(int x) {
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    int unite(int x, int y) {
        int rx = root(x), ry = root(y);
        if (rx == ry) return rx;
        ngroup--;
        if (siz[rx] > siz[ry]) swap(rx, ry);
        par[rx] = ry; siz[ry] += siz[rx]; mn[ry] = min(mn[rx], mn[ry]);
        return ry;
    }

    bool same(int x, int y) {
        int rx = root(x), ry = root(y);
        return rx == ry;
    }

    int size(int x) {return siz[root(x)];}
    int mindex (int x) {return mn[root(x)];} //xを含む連結成分の最小の頂点番号
    int group_count() {return ngroup;}

    vector<vector<int>> groups(){
        vector<int> rev(N); int nrt=0;
        for (int i=0; i<N; i++) if (root(i) == i) rev[i] = nrt, nrt++;
        vector<vector<int>> res(nrt);
        for (int i=0; i<N; i++) res[rev[root(i)]].push_back(i);

        return res;
    }
};

int main(){

    int N, M, x, y, cnt=0;
    cin >> N >> M;
    vector<vector<int>> E(N);
    UnionFind tree(N);
    vector<int> g(N), color(N, -1);
    string S;
    vector<pair<int, int>> a, b;
    for (int i=0; i<M; i++){
        cin >> x >> S >> y; x--; y--;
        if (S == "<==>") a.push_back({x, y});
        else b.push_back({x, y});
    }
    for (auto [x, y] : b){
        E[x].push_back(y);
        E[y].push_back(x);
    }

    auto dfs=[&](auto self, int from, int c)->void{
        color[from] = c;
        g[from] = cnt;
        for (auto to : E[from]){
            if (color[to] != -1){
                if (color[from] == color[to]){
                    cout << "No" << endl;
                    exit(0);
                }
                else continue;
            }
            self(self, to, 1-c);
        }
    };

    for (int i=0; i<N; i++){
        if (color[i] == -1){
            dfs(dfs, i, 0);
            cnt++;
        }
    }

    for (auto [x, y] : a){
        if (color[tree.root(x)] == -1 && color[tree.root(y)] == -1) tree.unite(x, y);
        else if (color[tree.root(x)] != -1 && color[tree.root(y)] != -1){
            if (color[tree.root(x)] != color[tree.root(y)]){
                cout << "No" << endl;
                return 0;
            }
        }
        else if (color[tree.root(x)] == -1 && color[tree.root(y)] != -1){
            color[tree.root(x)] = color[tree.root(y)];
        }
        else{
            color[tree.root(y)] = color[tree.root(x)];
        }
    }

    vector<int> ans, aa, bb;
    for (int i=0; i<N; i++){
        if (color[tree.root(i)] == -1) ans.push_back(i);
        else if (color[tree.root(i)] == 0) aa.push_back(i);
        else bb.push_back(i);
    }
    if (aa.size() < bb.size()) swap(aa, bb);
    for (auto x : aa) ans.push_back(x);
    cout << "Yes" << endl;
    sort(ans.begin(), ans.end());
    cout << ans.size() << endl;
    for (auto x : ans) cout << x+1 << " ";
    cout << endl;

    return 0;
}