#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <unordered_map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

vector< vector<int> > P;
vector<int> A;
vector<int> B;

void func( int a ) {
    B[a] = 1;

    for ( int i = 0; i < P[a].size(); i++ ) {
        int n = P[a][i];
        if ( B[n] == 0 ) {
            func(n);
        }
    }
}

int main() {
    
    int N,M;
    cin >> N >> M;

    P.resize(N);
    A.resize(N,0);
    B.resize(N,0);

    int s;

    for ( int i = 0; i < M; i++ ) {
        int a,b;
        cin >> a >> b;        
        P[a].push_back(b);
        P[b].push_back(a);

        A[a] = 1;
        A[b] = 1;

        s = a;
    }

    bool ans = true;

    func(s);

    for ( int i = 0; i < N; i++ ) {
        if ( A[i] != B[i] ) { ans = false; }
    }

    int a = 0;
    for ( int i = 0; i < N; i++ ) {
        if ( A[i] && P[i].size()%2 ) {
            a++;
        }
    }
    if ( !( a == 0 || a == 2 ) ) { ans = false; }

    cout << ( ans ? "YES" : "NO" ) << endl;

    return 0;
}