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

int N, M;

struct Node {
	int cnt=INT32_MAX;
};

int main()
{
	cin >> N >> M;
	vector<vector<int> > G(N+1);
	vector<Node> node(N + 1); node[1].cnt = 0;
	for (int i = 0; i < M; i++) {
		int a, b; cin >> a >> b;
		G[a].push_back(b);
		G[b].push_back(a);
	}

	queue<int> que;
	for (int i = 0; i < G[1].size(); i++) {
		que.push(G[1][i]);
		node[G[1][i]].cnt = node[1].cnt + 1;
	}

	bool flag = false;
	while (!que.empty()) {
		int p = que.front(); que.pop();
		for (int i = 0; i < G[p].size(); i++) {
			if (node[G[p][i]].cnt == 2 && node[p].cnt == 2) flag = true;
			if (node[G[p][i]].cnt < node[p].cnt)continue;
			que.push(G[p][i]);
			node[G[p][i]].cnt = node[p].cnt + 1;
		}
	}
	if (flag)cout << "YES" << endl;
	else cout << "NO" << endl;

    return 0;
}