#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
using namespace std;

struct UnionFind
{
	vector<int> par;
	vector<int> sizes;

	UnionFind(int n) : par(n), sizes(n, 1) {
		for (int i = 0; i < n; i++) par[i] = i;
	}

	int find(int x) {
		if (x == par[x])return x;
		return par[x] = find(par[x]);
	}

	void unite(int x, int y) {
		x = find(x);
		y = find(y);

		if (x == y) return;

		if (sizes[x] < sizes[y]) swap(x, y);

		par[y] = x;
		sizes[x] += sizes[y];
	}

	bool same(int x, int y) {
		return find(x) == find(y);
	}

	int size(int x) {
		return sizes[find(x)];
	}
};

int main()
{
	int N, M; cin >> N >> M;
	vector<vector<int>>E(N);
	UnionFind uf(N);
	vector<int>used;
	for (int i = 0; i < M; i++) {
		int a, b; cin >> a >> b;
		E[a].push_back(b);
		E[b].push_back(a);

		uf.unite(a, b);
		used.push_back(a);
		used.push_back(b);
	}

	int cnt = 0;
	for (int i = 0; i < N; i++) {
		if (E[i].size() % 2)cnt++;
	}

	bool flag = true;
	for (int i = 0; i < used.size() - 1; i++) {
		if (!uf.same(used[i], used[i + 1]))flag = false;
	}

	if (flag && (cnt == 2 || cnt == 0))cout << "YES" << endl;
	else cout << "NO" << endl;

    return 0;
}