#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
//#define int long long
using namespace std;

int N, M;
vector<int> G[2 * 10000];
int A, B;

//i:辺をたどった回数, j:今いる頂点, checked:通った頂点の集合
bool rec(int i, int j, set<int> checked)
{
	/*
	printf("rec(%d, %d, set)\n", i, j);
	set<int>::iterator it = checked.begin();
	while (it != checked.end())
	{
		cout << *it << ", " << endl;
		it++;
	}
	*/

	if (i == 5)
	{
		if (j == 0) return true;
		else return false;
	}

	if (j != 0)
	{
		checked.insert(j);
	}

	bool ret = false;
	rep(ii,G[j].size())
	{
		if (checked.find(G[j][ii]) == checked.end())
		{
			//次の頂点がまだ未探索の場合
			//checked.insert(G[j][i]);
			ret = ret || rec(i + 1, G[j][ii], checked);
			//checked.erase(G[j][i]);
		}
	}

	return ret;
}

signed main()
{
	cin >> N >> M;
	rep(i,M)
	{
		cin >> A >> B;
		A--; B--;
		G[A].push_back(B);
		G[B].push_back(A);
	}

	set<int> checked;
	if (rec(0, 0, checked))
	{
		cout << "YES" << endl;
	} else {
		cout << "NO" << endl;
	}
}