#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
const int mod=998244353;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a,bool upp=0){if(a) cout<<(upp?"YES\n":"Yes\n"); else cout<<(upp?"NO\n":"No\n");}
template<class T> void vec_out(vector<T> &p,int ty=0){
if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}


namespace po167{
struct UFtree
{
    using _F=int;
    int _n;
    std::vector<_F> wei;
    std::vector<int> q;
    int component;
    UFtree(int n):_n(n),wei(n),component(n),par(n){
        for(int i=0;i<n;i++){
            wei[i]=1,par[i]=i;
        }
    }
    void intialize(){
        for(auto x:q){
            wei[root(x)]=1;
            par[x]=x;
        }
        component=(int)par.size();
        q={};
    }
    //根っこを返す
    int root(int a){
        assert(0<=a&&a<_n);
        if(a==par[a]) return a;
        return par[a]=root(par[a]);
    }
    //trueなら1,falseなら0
    int same(int a,int b){
        assert(0<=a&&a<_n);
        assert(0<=b&&b<_n);
        if(root(a)==root(b)) return 1;
        else return 0;
    }
    _F size(int a){
        return wei[root(a)];
    }
    //a,bが違う根っこの元なら結合する,結合したらtrueを返す
    bool unite(int a,int b){
        a=root(a),b=root(b);
        if(a==b) return false;
        if(wei[a]<wei[b]) std::swap(a,b);
        par[b]=a;
        q.push_back(b);
        wei[a]+=wei[b];
        component--;
        return true;
    }
    private:
    std::vector<int> par;
};
}
using po167::UFtree;



void solve();
// oddloop
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int t=1;
    //cin>>t;
    rep(i,0,t) solve();
}

void solve(){
    int N,M;
    cin>>N>>M;
    UFtree T(N*2);
    rep(i,0,M){
        int a,b;
        cin>>a>>b;
        a--,b--;
        T.unite(a,b+N);
        T.unite(a+N,b);
    }
    bool ok=1;
    rep(i,0,N) if(T.same(i,i+N)) ok=0;
    yneos(ok);
}