/* -*- coding: utf-8 -*-
 *
 * 408.cc: No.408 五輪ピック - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 20000;

/* typedef */

typedef vector<int> vi;
typedef set<int> si;

/* global variables */

vi nbrs[MAX_N];
si rs[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int ai, bi;
    cin >> ai >> bi;
    ai--, bi--;
    nbrs[ai].push_back(bi);
    nbrs[bi].push_back(ai);
  }

  vi &nbr0 = nbrs[0];
  for (vi::iterator vit0 = nbr0.begin(); vit0 != nbr0.end(); vit0++) {
    int &v1 = *vit0;
    vi &nbr1 = nbrs[v1];
    for (vi::iterator vit1 = nbr1.begin(); vit1 != nbr1.end(); vit1++) {
      int &v2 = *vit1;
      if (v2 != 0) rs[v2].insert(v1);
    }
  }    

  bool ok = false;

  for (int u = 1; u < n; u++) {
    si &ru = rs[u];
    if (ru.size() == 0) continue;

    vi &nbru = nbrs[u];
    for (vi::iterator vit = nbru.begin(); vit != nbru.end(); vit++) {
      int &v = *vit;
      si &rv = rs[v];
      if (u >= v || rv.size() == 0) continue;

      si::iterator situ = ru.begin(), sitv = rv.begin();
      while (! ok) {
	while (situ != ru.end() && (*situ == v || *situ == *sitv)) situ++;
	if (situ == ru.end()) break;
	while (sitv != rv.end() && (*sitv == u || *sitv == *situ)) sitv++;
	if (sitv == rv.end()) break;

	if (*situ != v && *sitv != u && *situ != *sitv) ok = true;
      }
      if (ok) break;
    }
    if (ok) break;
  }

  cout << (ok ? "YES" : "NO") << endl;
  return 0;
}