#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <utility>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef  long long ll;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define  MP make_pair
#define  PB push_back
#define inf  1000000007

long long  mod = 1000000007;

int p[2000];

void init(int n){
    for (int i = 0; i < n; ++i) {
        p[i]=i;
    }
}


int find(int x){
	if(x != p[x]){
		p[x] = find(p[x]);
    	}
    	return p[x];
    }
     
void union_set(int x,int y){
	x = find(x);
	y = find(y);
	if(x==y) return;
	p[x]=y;
	return ;
}


int main(){
	int n,m;
	cin >> n >> m;
	vector<vector<int> >v(n);
	set<int> st;
	init(n);
	for(int i=0;i<m;i++){
		int a,b;
		cin >> a >> b;
		v[a].push_back(b);
		v[b].push_back(a);
		union_set(a,b);
		st.insert(a);
		st.insert(b);
	}
	int x = 0;
	for(int i=0;i<n;i++){
		if(v[i].size()%2==1)x++;
	}
	if(x>=3){
		cout << "NO" << endl;
		return 0;
	}
	int z = -1;
	bool flag = 0;
	for(int i=0;i<n;i++){
		if(v[i].size()!=0){
			if(z==-1){
				z = find(i);
			}else{
				if(z!=find(i)){
					flag = 1;
				}
			}
		}
	}
	if(flag){
		cout << "NO" << endl;
	}else{
		cout << "YES" << endl;
	}
	return 0;
}