#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#define REP(i, m, n) for(int i=int(m);i<int(n);i++)
#define EACH(i, c) for (auto &(i): c)
#define all(c) begin(c),end(c)
#define EXIST(s, e) ((s).find(e)!=(s).end())
#define SORT(c) sort(begin(c),end(c))
#define pb emplace_back
#define MP make_pair
#define SZ(a) int((a).size())

//#define LOCAL 0
//#ifdef LOCAL
//#define DEBUG(s) cout << (s) << endl
//#define dump(x)  cerr << #x << " = " << (x) << endl
//#define BR cout << endl;
//#else
//#define DEBUG(s) do{}while(0)
//#define dump(x) do{}while(0)
//#define BR
//#endif


//改造
typedef long long int ll;
using namespace std;
#define INF (1 << 20)
#define INFl (ll)5e15
#define DEBUG 0 //デバッグする時1にしてね

//ここから編集する
class UnionFind {
    vector<int> p;//p[i]はiの属する組織
public:
    UnionFind(int n){
        p = vector<int>(n);
        for(int i = 0; i < n; i++){
            p[i] = i;
        }
        return;
    }

    void printState() {
        if (DEBUG) {
            cout << "---" << endl;
            for (int i = 0; i < p.size(); i++) {
                printf("%dの親は%d\n", i, p[i]);
            }
            cout << "---" << endl;
        }
    }

/* xの属する集合を返す */
    int find(int x) {
        if (p[x] == x) return x;
        return p[x] = find(p[x]);
    }

/* yにxを統合する */
    void unite(int x, int y) {
        p[find(x)] = p[find(y)];
    }

/* xとyが属する集合が同じかを判定する */
    bool same(int x, int y) {
        return find(x) == find(y);
    }

};


int main() {
    int N,M;
    cin >> N >> M;
    vector<int> dim(N,0);
    vector<int> a(M),b(M);
    UnionFind u(N);
    REP(i,0,M){
        cin >> a[i] >> b[i];
        dim[a[i]]++;
        dim[b[i]]++;
        u.unite(a[i],b[i]);
    }


    REP(i,0,M){
        REP(j,0,M){
            if(i != j){
                if(!u.same(a[i],a[j])){
                    cout << "NO" << endl;
                    return 0;
                }
            }
        }
    }
    int cnt = 0;
    REP(i,0,N){
        if(dim[i] % 2 == 1){
            cnt++;
        }
    }
    if(cnt == 0 || cnt == 2){
        cout << "YES" << endl;
    }else{
        cout << "NO" << endl;
    }

    return 0;
}