#include <iostream>
#include <stdio.h>
#include <cstring>
#include <math.h>
#include <algorithm>
#include <vector>
#include <string>
#include <stdlib.h>
#include <queue>
#include <stack>
#include <utility>
#define rep(i,n) for(int i=0;i<n;i++)
#define rrep(i,n) for(int i=n-1;i>=0;i--)
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define ll long long
#define INF 1000000001
#define mod 1000000007
using namespace std;

int main(){
	//cin.tie(0);
	//ios::sync_with_stdio(false);
	

	int n,m;
	cin>>n>>m;
	vector<vector<int>> s(n);
	int a,b;
	rep(i,m){
		cin>>a>>b;
		s[a].push_back(b);
		s[b].push_back(a);
	}
	//連結
	vector<int> check(n);
	rep(i,n){
		check[i]=-1;
	}
	a=0;
	b=0;
	int aa=1;
	while(aa){
		stack<int> sta;
		sta.push(a);
		check[a]=b;
		while(sta.empty()==0){
			int x=sta.top();
			sta.pop();
			rep(i,s[x].size()){
				if(check[s[x][i]]==-1){
					sta.push(s[x][i]);
					check[s[x][i]]=b;
				}
			}
		}
		b++;
		rep(i,n){
			if(check[i]==-1){
				a=i;
				break;
			}
			if(i==n-1){
				aa=0;
			}
		}
	}
	vector<int> y(n);
	rep(i,n){
		y[i]=0;
	}
	rep(i,n){
		y[check[i]]++;
	}
	int z=0;
	rep(i,y.size()){
		if(y[i]>1 && z==0){
			z=1;
		}else if(y[i]>1 && z==1){
			cout<<"NO"<<endl;
			return 0;	
		}
	}
	int cc=0;
	rep(i,n){
		if(s[i].size()%2==1){
			cc++;
		}
	}
	if(cc>2){
		cout<<"NO"<<endl;
	}else{
		cout<<"YES"<<endl;
	}


}