#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>
#include <queue>
using namespace std;
int ct[500],n,m,st;
bool vis[500];
vector<int> G[500];
int main() {
	cin >> n >> m;
	memset(vis, true, sizeof(vis));
	for (int i = 0; i < m; i++) {
		int a, b; cin >> a >> b; 
		vis[a] = false; vis[b]=false;
		st = a;
		G[a].push_back(b); G[b].push_back(a);
		ct[a]++; ct[b]++;
	}
	int oct = 0;
	for (int i = 0; i < n; i++) { if (ct[i] % 2 == 1)oct++; }
	queue<int> q; q.push(st); vis[st] = true;
	while (!q.empty()) {
		int ci = q.front(); q.pop();
		for (int i = 0; i < G[ci].size(); i++) { if (vis[G[ci][i]])continue; vis[G[ci][i]] = true; q.push(G[ci][i]); }
	}
	for (int i = 0; i < n; i++) { if (!vis[i])oct = 100; }
	if (oct == 0 || oct == 2)cout << "YES" << endl;
	else cout << "NO" << endl;
	return 0;
}