#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define FORR(x, arr) for(auto& x:arr)
#define ITR(x, c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;
typedef pair<int, int> P;

int n, m;
vector<int> g[510];

template<int um> class UF {
	public:
	vector<int> par,rank,cnt;
	UF() {par=rank=vector<int>(um,0); cnt=vector<int>(um,1); for(int i=0;i<um;i++) par[i]=i;}
	void reinit() {for(int i=0;i<um;i++) rank[i]=0,cnt[i]=1,par[i]=i;}
	int operator[](int x) {return (par[x]==x)?(x):(par[x] = operator[](par[x]));}
	int count(int x) { return cnt[operator[](x)];}
	int operator()(int x,int y) {
		if((x=operator[](x))==(y=operator[](y))) return x;
		cnt[y]=cnt[x]=cnt[x]+cnt[y];
		if(rank[x]>rank[y]) return par[x]=y;
		rank[x]+=rank[x]==rank[y]; return par[y]=x;
	}
};
UF<510> uf;

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> n >> m;
	set<int> st;
	FOR(i, m) {
		int a, b;
		cin >> a >> b;
		g[a].push_back(b);
		g[b].push_back(a);
		st.insert(a);
		st.insert(b);
		uf(a, b);
	}
	int cnt = 0;
	FOR(i, n) {
		if (g[i].size() & 1) cnt++;
	}
	FOR(i, n) {
		if (uf.count(i)!=1 && uf.count(i)!=st.size()) cnt = -1;
	}
	cout << (cnt==0 || cnt==2 ? "YES" : "NO") << endl;
	return 0;
}