#include <bits/stdc++.h>
using namespace std;

using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using LL = long long;
using VL = vector<LL>;
using VVL = vector<VL>;
using PLL = pair<LL, LL>;
using VS = vector<string>;

#define ALL(a)  begin((a)),end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

#define FF first
#define SS second
template<class S, class T>
istream& operator>>(istream& is, pair<S,T>& p){
  return is >> p.FF >> p.SS;
}
template<class S, class T>
ostream& operator<<(ostream& os, const pair<S,T>& p){
  return os << p.FF << " " << p.SS;
}
template<class T>
void maxi(T& x, T y){
  if(x < y) x = y;
}
template<class T>
void mini(T& x, T y){
  if(x > y) x = y;
}


const double EPS = 1e-10;
const double PI  = acos(-1.0);
const LL MOD = 1e9+7;

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int N, M;
  cin >> N >> M;
  vector<vector<PII>> G(N);
  vector<PII> es(M);
  REP(i,M){
	int a, b;
	cin >> a >> b;
	G[a].EB(b,i);
	G[b].EB(a,i);
	es[i] = MP(a, b);
  }

  vector<bool> vis(M);
  queue<int> q;
  q.push(0);
  vis[0] = true;
  while(!q.empty()){
	int i = q.front();
	q.pop();
	for(auto& e: G[es[i].FF]){
	  if(vis[e.SS]) continue;
	  vis[e.SS] = true;
	  q.push(e.SS);
	}
	for(auto& e: G[es[i].SS]){
	  if(vis[e.SS]) continue;
	  vis[e.SS] = true;
	  q.push(e.SS);
	}
  }
  int odd = 0;
  REP(i,N) odd += SZ(G[i]) % 2;

  if(count(ALL(vis), true) != M || M > 2)
	cout << "NO" << endl;
  else
	cout << "YES" << endl;

  return 0;
}