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

int main() {
	int N, M;
	cin >> N >> M;
	vector<int> graph[20050];
	int A[50010] = { 0 }, B[50010] = { 0 };
	for (int i = 0; i < M; i++)
	{
		int a, b;
		cin >> a >> b;
		A[i] = a, B[i] = b;
		
			graph[a].push_back(b);
			graph[b].push_back(a);
		}
		
	
	

	/*for (int i = 0; i <= N; i++)
	{
		cout << i << " " ;
		for (int j = 0; j < graph[i].size(); j++)
		{
			cout << graph[i][j]<<" ";
		}
		cout << endl;
	}
	*/
	vector<unordered_set<int>> p(N+1);
	for (int i = 0; i < graph[1].size(); i++)
	{
		int a = graph[1][i];
		for (int j = 0; j < graph[a].size(); j++)
		{
			int b = graph[a][j];
			if (b == 1)
				continue;
			p[b].insert(a);
			//cout << a << " " << b << endl;
		}
	}
/*	for (int i = 0; i  < p.size(); i++)
	{
		for (int j = i; j < p.size(); j++)
		{

			if (i == j)
				continue;
			int a1 = p[i].first, b1 = p[i].second, a2 = p[j].first, b2 = p[j].second;
			if (a1 == a2 || b1 == b2 || a2 == b1 || a1 == b2)
				continue;
			bool flag = false;
			for (int j = 0; j < graph[b1].size(); j++)
			{
				if (graph[b1][j] == b2)
					flag = true;
			}
			if (flag) {
				//	cout << a1 << " " << b1 << " " << a2 << " " << b2 << endl;
				cout << "YES" << endl;
				return 0;
			}
		}
	}
	*/
	for (int i = 0; i < M; i++)
	{
		int c = A[i], d = B[i];
		for (int j = 0; j < graph[c].size(); j++)
		{
			if (d == graph[c][j]) {
				for (auto &s : p[c]) {
					for (auto &t : p[d]) {
						if (s != t && s != c && s != d && t!= c&&t != d) {
							cout << "YES" << endl;
							//cout << s << " " << t << " "<<c<<" "<<d<<endl;
							return 0;
						}
					}
				}
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}