#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

class UnionFind{
  int n;
  vector<int> data;
public:
  UnionFind(int _n):n(_n),data(_n,-1){}
  bool link(int a, int b){ //if new link, then true.
    int ra=find_root(a);
    int rb=find_root(b);
    if(ra!=rb){
      if(data[rb]<data[ra]) swap(ra,rb);
      data[ra]+=data[rb];
      data[rb]=ra;
    }
    return (ra!=rb);
  }
  bool check(int a, int b){ //if same set, then true.
    return (find_root(a)==find_root(b));
  }
  int find_root(int a){
    return ((data[a]<0)?a:(data[a]=find_root(data[a])));
  }
};

int main(){
  int N, M;
  cin >> N >> M;
  vector<int> v(N,0);
  UnionFind uf(N);
  int idx = 0;
  rep(i,M){
    int a, b;
    cin >> a >> b;
    v[a]++;
    v[b]++;
    idx = a;
    uf.link(a,b);
  }

  bool flg = true;
  rep(i,v.size()){
    if(v[i]>0 && !uf.check(idx,i)) flg = false;
  }
  
  int odd = 0;
  rep(i,v.size()){
    if(v[i]%2==1) odd++;
  }

  if(flg && (odd == 0 || odd == 2)){
    cout << "YES" << endl;
  }else{
    cout << "NO" << endl;
  }
  
  return 0;
}