#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define ALL(c) (c).begin(), (c).end()

typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef vector<VI> VVI;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

VI e[500];
int visit[500];

void dfs(int now){
    visit[now] = 1;
    for (int next : e[now]){
        if (!visit[next]) dfs(next);
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    VI c(n);
    REP(i,m){
        int u, v;
        cin >> u >> v;
        c[u]++;
        c[v]++;
        e[u].push_back(v);
        e[v].push_back(u);
    }

    int odd = 0;
    REP(i,n) odd += c[i] % 2;

    REP(i,n){
        if (c[i]){
            dfs(i);
            break;
        }
    }

    bool connect = true;
    REP(i,n) if (c[i] && !visit[i]) connect = false;

    cout << ((odd == 0 || odd == 2) && connect ? "YES" : "NO") << endl;

    return 0;
}