#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;


// change!!!!!!!!!!!!
#define MAX_N 500

int uf_par[MAX_N];
int uf_rank[MAX_N];

void uf_init( int n ) {
    for ( int i = 0; i < n; i++ ) {
        uf_par[i] = i;
        uf_rank[i] = 0;
    }
}

int uf_find( int x ) {
    if ( uf_par[x] == x ) { return x; }
    else { return uf_par[x] = uf_find(uf_par[x]); }
}

void uf_unite( int x, int y ) {
    x = uf_find( x );
    y = uf_find( y );
    if ( x == y ) { return; }
    
    if ( uf_rank[x] < uf_rank[y] ) {
        uf_par[x] = y;
    }
    else {
        uf_par[y] = x;
        if ( uf_rank[x] == uf_rank[y] ) { uf_rank[x]++; }
    }
    
}

bool uf_same( int x, int y ) {
    return uf_find(x) == uf_find(y);
}

int main() {
    int N,M;
    cin >> N >> M;
    
    vector< vector<int> > P(N);

    uf_init(N);

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

    bool ans = true;

    int a = INT_MAX;
    for ( int i = 0; i < N; i++ ) {
        if ( uf_find(i) != i ) {
            if ( a != INT_MAX && a != uf_find(i) ) { ans = false; break; }
            a = uf_find(i);
        }
    }  

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


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

    return 0;
}