#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>
#include <set>
#include <map>
#include <cmath>
#include <queue>
#include <cstdio>
#include <limits>
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if(a < b){ a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if(a > b){ a = b; return 1; } return 0; }
using ll = long long; using ld = long double;
using pi = pair<int,int>; using pl = pair<ll,ll>;
using vi = vector<int>; using vii = vector<vi>;
using vl = vector<ll>; using vll = vector<vl>;
const int inf = numeric_limits<int>::max();
const ll infll = numeric_limits<ll>::max();
struct UFT{
  vector<int> par;//親
  vector<int> rank;//木の深さ
  vector<int> size;//木の大きさ
  int n;
  
  UFT(int _n)
  {
    n = _n;
    par.resize(n);
    rank.assign(n,0);
    size.assign(n,0);
    rep(i,n){
      par[i] = i;
    }
  }
  
  //xの根を返す
  int find(int x)
  {
    if(par[x] == x) return x;
    else return par[x] = find(par[x]);
  }

  //x,yを併合
  void unite(int x,int y)
  {
    x = find(x);
    y = find(y);
    if(x == y) return;

    if(rank[x] < rank[y]){
      par[x] = y;
      size[y] += size[x];
    }
    else{
      par[y] = x;
      size[x] += size[y];
      if(rank[x] == rank[y]) rank[x]++;
    }
  }

  //x,yが同じグループにいるかどうかを返す
  bool same(int x,int y)
  {
    return find(x) == find(y);
  }

  //xの属する木のサイズを探す
  int usize(int x)
  {
    return size[find(x)];
  }
};


//****************************************
// Graph template
//****************************************

// status of edge
template <typename X>
struct Edge{
  int from;
  int to;
  X cost;

  Edge() = default;

  Edge(int from, int to, X cost) : from(from), to(to), cost(cost) {}
};

// status of node
template <typename X>
struct Node{ 
  int idx;
  vector<Edge<X>> edge;
  
  Node() = default;

  explicit Node(int idx) : idx(idx) {}
};

template <typename X>
class Graph{
private:
  int n; // number of node
  int m; // number of edge
  vector<Node<X>> node; 

  void Init_Node() {
    rep(i,n) node.emplace_back(i);
  }
public:
  explicit Graph(int n) : n(n) {
    Init_Node();
  }

  // edges have no-weight 
  Graph(int n, int m, vector<int> from, vector<int> to) : n(n), m(m) {
    Init_Node();
    rep(i,m) {
      add_edge(from[i], to[i]);
      add_edge(to[i], from[i]);      
    }
  }  

  // edges have weight
  Graph(int n, int m, vector<int> from, vector<int> to, vector<X> cost) : n(n), m(m) {
    Init_Node();
    rep(i,m) {
      add_edge(from[i], to[i], cost[i]);
      add_edge(to[i], from[i], cost[i]);      
    }
  }

  void add_edge(int from, int to, X cost = 1) {
    node[from].edge.emplace_back(from, to, cost);
  }

  // オイラー閉路があるか？
  bool EulerCheck() {
    bool res = true;
    rep(i,n) {
      int a = node[i].edge.size();
      if(a % 2 == 1) res = false;
    }
    return res;
  }

  // s->tのオイラー路があるか？
  bool EulerCheck(int s, int t) {
    bool res = true;
    rep(i,n) {
      if(i == s || i == t) continue;
      int a = node[i].edge.size();
      if(a % 2 == 1) res = false;
    }
    return res;
  }  
  
};


int main()
{
  int n,m; cin >> n >> m;
  vi a(m), b(m);
  UFT uf(n);
  vector<bool> f(n, false);
  rep(i,m) {
    cin >> a[i] >> b[i];
    uf.unite(a[i], b[i]);
    f[a[i]] = f[b[i]] = true;
  }

  Graph<int> gp(n, m, a, b);
  rep(i,n) {
    rep(j,n) {
      if(i >= j) continue;
      if( !f[i] || !f[j] ) continue;
      if( !uf.same(i, j) ) {
	cout << "NO" << "\n";
	return 0;
      }
      if(gp.EulerCheck(i, j)) {
	cout << "YES" << "\n";
	return 0;
      }
    }
  }
  cout << "NO" << "\n";
  return 0;
}