#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(int (i) = (s);(i) <= (e);(i)++)


bool used[505][505];

int main(){
  int N;
  cin >> N;
  int M;
  cin >> M;
  vector<int> cnt(N,0);

  vector<vector<int>> G(N);



  int start = 0;
  rep(i,0,M - 1){
    int a,b;
    cin >> a >> b;
    cnt[a]++;
    cnt[b]++;
    start = b;
    G[a].push_back(b);
    G[b].push_back(a);
    used[min(a,b)][max(a,b)] = 1;
  }

  int c =0;
  queue<int> que;
  que.push(start);
  vector<bool> vis(N,0);
  vis[start] = 1;
  while(!que.empty()){
    int v = que.front();
    que.pop();

    for(int to : G[v]){
      c += used[min(v,to)][max(v,to)];
      used[min(v,to)][max(v,to)] = 0;
      if(vis[to]) continue;
      vis[to] = 1;
      que.push(to);
    }
  }


  int ans = 0;
  rep(i,0,N - 1){
    ans += cnt[i] % 2;
  }
  if(c == M && ans == 0 || ans == 2){
    cout << "YES" << endl;
  }
  else{
    cout << "NO" << endl; }
}