#include <bits/stdc++.h>

using namespace std;
#define int long long
const int maxn=1e6+5;
vector<pair<int,int> > a[maxn];
bool used[maxn];
int c[2];vector<int> g;int col[maxn];
void dfs(int x)
{
    used[x]=true;g.push_back(x);
    c[col[x]]++;
    for(auto [v,w]:a[x])
    {
        if(!used[v])
        {
            col[v]=(col[x]^w);
            dfs(v);
        }
    }
}
int32_t main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int n,m;cin>>n>>m;
    for(int i=0;i<m;++i)
    {
        int x;string s;int y;cin>>x>>s>>y;--x;--y;
        if(s[2]=='=') {a[x].push_back({y,0});a[y].push_back({x,0});}
        else {a[x].push_back({y,1});a[y].push_back({x,1});}
    }
    for(int i=0;i<n;++i)
    {
        if(!used[i])
        {
            g.clear();c[0]=0;c[1]=0;
            dfs(i);
            if(c[1]<c[0])
            {
                for(int i:g) col[i]^=1;
            }
        }
    }
    for(int i=0;i<n;++i) for(auto [x,w]:a[i]) if((col[i]^col[x])!=w) {puts("No");exit(0);}
    int s=accumulate(col,col+n,0LL);
    if(2*s==n) {puts("No");exit(0);}
    cout<<"Yes"<<endl;
    cout<<s<<endl;
    for(int i=0;i<n;++i) if(col[i]) cout<<i+1<<' '; cout<<endl;
    return 0;
}