#include <cmath>
#include <string>
#include <vector>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
int n, m, a, b, d[509], par[509];
int root(int x) { return x == par[x] ? x : par[x] = root(par[x]); }
int main() {
	cin >> n >> m;
	for (int i = 0; i < n; i++) par[i] = i;
	for (int i = 0; i < m; i++) {
		cin >> a >> b;
		d[a]++; d[b]++;
		par[root(a)] = root(b);
	}
	vector<int> s;
	for (int i = 0; i < n; i++) {
		if (d[i] >= 1) s.push_back(root(i));
	}
	sort(s.begin(), s.end());
	bool ret = true;
	for (int i = 1; i < s.size(); i++) {
		if (s[i - 1] != s[i]) ret = false;
	}
	int cnt = 0;
	for (int i = 0; i < n; i++) {
		if (d[i] % 2 == 1) cnt++;
	}
	cout << (cnt >= 3 || !ret ? "NO" : "YES") << endl;
	return 0;
}