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

#define DEBUG(x) cout<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cout<<#v<<":";for(int i=0;i<v.size();i++) cout<<" "<<v[i]; cout<<endl

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
const int inf = 1000000001;
const ll INF = 1e18 * 4;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846
#define Sp(p) cout<<setprecision(15)<<fixed<<p<<endl;
int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };

#define N 160
vi par(N); //親
vi ran(N); //木の深さ

			   //n要素で初期化
void init(int n) {
	int i;
	for (i = 0; i < n; i++) {
		par[i] = i;
		ran[i] = 0;
	}
}

//木の根を求める
int find(int x) {
	if (par[x] == x) {
		return x;
	}
	else {
		return par[x] = find(par[x]);
	}
}

//xとyの属する集合を併合
void unite(int x, int y) {
	x = find(x);
	y = find(y);
	if (x == y) {
		return;
	}
	if (ran[x]<ran[y]) {
		par[x] = y;
	}
	else {
		par[y] = x;
		if (ran[x] == ran[y]) {
			ran[x]++;
		}
	}
}

//xとyが同じ集合に属するか否か
bool same(int x, int y) {
	return find(x) == find(y);
}

int main() {
	int n, m, i;
	cin >> n >> m;
	init(n);
	vi num(n);
	for (i = 0; i < m; i++) {
		int s1, s2;
		cin >> s1 >> s2;
		num[s1]++; num[s2]++;
		unite(s1, s2);
	}
	int s;
	for (i = 0; i < n; i++) {
		if (num[i]) {
			s = i;
			break;
		}
	}
	for (i = 0; i < n; i++) {
		if (num[i]) {
			if (!same(s, i)) {
				cout << "NO" << endl;
				return 0;
			}
		}
	}

	int cnt = 0;
	for (i = 0; i < n; i++) {
		if (num[i] % 2) {
			cnt++;
		}
	}
	if (cnt == 0 || cnt == 2) {
		cout << "YES" << endl;
	}
	else {
		cout << "NO" << endl;
	}
}