#include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <numeric>
#include <utility>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <unordered_map>
using namespace std;

#define REP(i, s) for (int i = 0; i < s; ++i)
#define ALL(v) (v.begin(), v.end())
#define COUT(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << endl
#define EACH(i, s) for (__typeof__((s).begin()) i = (s).begin(); i != (s).end(); ++i)

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T1, class T2> ostream& operator << (ostream &s, pair<T1,T2> P)
{ return s << '<' << P.first << ", " << P.second << '>'; }
template<class T> ostream& operator << (ostream &s, vector<T> P)
{ for (int i = 0; i < P.size(); ++i) { if (i > 0) { s << " "; } s << P[i]; } return s; }
template<class T> ostream& operator << (ostream &s, vector<vector<T> > P)
{ for (int i = 0; i < P.size(); ++i) { s << endl << P[i]; } return s << endl; }
template<class T> ostream& operator << (ostream &s, set<T> P)
{ EACH(it, P) { s << "<" << *it << "> "; } return s << endl; }
template<class T1, class T2> ostream& operator << (ostream &s, map<T1,T2> P)
{ EACH(it, P) { s << "<" << it->first << "->" << it->second << "> "; } return s << endl; }

typedef long long  ll;

#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))

const int nmax=510;

bool vis[nmax];
vector<int>w[nmax];
void dfs(int v){
    vis[v]=true;
    for(int i : w[v]){
        if(!vis[i]){
            dfs(i);
        }
    }
}

int main() {
    int n,m;
    cin>>n>>m;
    int start=-1;
    vector<int>deg(n,0);
    for(int i=0;i<m;i++){
        int a,b;
        cin>>a>>b;
        w[a].push_back(b);
        w[b].push_back(a);
        deg[a]++;
        deg[b]++;
        start=a;
    }
    dfs(start);
    int cnt=0;
    for(int i=0;i<n;i++){
        cnt+=deg[i]%2;
        if(cnt>2 || (!vis[i] && (deg[i]>0))) {
            cout<<"NO"<<endl;
            return 0;
        }
    }
        cout<<"YES"<<endl;
        return 0;
    }