#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<pll, int> plp;
const ll INF = 1e9+100;
const ll MOD = 1e9+7;
const double EPS = 1e-10;
const bool debug = 0;
//--------------------------------//

struct UnionFind {
	vector<int> par, rank;
	
	UnionFind(int n) {
		par.resize(n);
		rank.resize(n);
		REP(i, n) {
		 par[i] = i;
		 rank[i] = 0;
		}
	}
	
	int operator[] (int x) {
		return find(x);
	}
	
	int find(int x) {
		if (x == par[x]) return x;
		return par[x] = find(par[x]);
	}
	
	void unite(int x, int y) {
		x = find(x); y = find(y);
		if (x == y) return;
		
		if (rank[x] < rank[y]) swap(x, y);
		
		par[y] = x;
		if (rank[x] == rank[y]) rank[x]++;
	}
	
	bool same(int x, int y) {
		return find(x) == find(y);
	}
	
};


int n, m;
int a[2500], b[2500];
int cnt[500];

int main() {
	cin >> n >> m;
	
	UnionFind uf(n);
	REP(i, m) {
		scanf("%d %d", a + i, b + i);
		cnt[a[i]]++; cnt[b[i]]++;
		uf.unite(a[i], b[i]);
	}
	
	int odd = 0;
	REP(i, n) {
		if (cnt[i] & 1) odd++;
	}
	
	bool ans = true;
	if (odd > 2 || odd == 1) ans = false;
	set<int> ss;
	REP(i, m) {
		ss.insert(uf[a[i]]);
		ss.insert(uf[b[i]]);
	}
	if (ss.size() != 1) ans = false;
	
	puts(ans ? "YES" : "NO");
	
	return 0;
}