#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <stdio.h>
using namespace std;
#define int long long
int MOD = 1000000007;
struct UnionFind {
	vector<int> data;
	UnionFind(int size) : data(size, -1) { }
	bool unionSet(int x, int y) {
		x = root(x); y = root(y);
		if (x != y) {
			if (data[y] < data[x]) swap(x, y);
			data[x] += data[y]; data[y] = x;
		}
		return x != y;
	}
	bool findSet(int x, int y) {
		return root(x) == root(y);
	}
	int root(int x) {
		return data[x] < 0 ? x : data[x] = root(data[x]);
	}
	int size(int x) {
		return -data[root(x)];
	}
};
signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N ,M;
	cin >> N >> M;
	vector<int> c(N, 0);
	int res = 0;
	int a, b;
	UnionFind uf(N);
	for (int i = 0; i < M; i++) {
		cin >> a >> b;
		
		c[a]++;
		c[b]++;
		
		uf.unionSet(a, b);
	}
	for (int i = 0; i < N; i++) {
		if (c[i] > 0) {
			a = uf.root(i);
			break;
		}
	}
	bool f = true;
	for (int i = 0; i < N; i++) {
		if (c[i] > 0 && a != uf.root(i)) {
			f = false;
			break;
		}
	}
	if (f) {
		int cc = 0;
		for (int i = 0; i < N; i++) {
			if (c[i] % 2 == 1) {
				cc++;
			}
		}
		if (cc != 0 && cc != 2) {
			f = false;
		}
	}
	if (f) {
		cout << "YES" << endl;
	}
	else {
		cout << "NO" << endl;
	}
	
}