fn.cpp

#include <iostream>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <string>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <utility>
#include <vector>
 
using namespace std;
 
#define DEBUG(x) cout << ">>> " #x << " : " << x << endl;
 
int main() {
	int n,m;
	while( scanf("%d %d", &n, &m) == 2 ) {
		map<int,int> neighbours;
		bool found = false;
 
 
		for( int i = 0; i < m; i++ ) {
			int u,v;
			scanf( "%d %d", &u, &v );
 
			if( ++neighbours[u] >= 4 ) { found = true; }
			if( ++neighbours[v] >= 4 ) { found = true; }
		}
 
		if( found ) {
			printf( "YES\n" );
		} else {
			printf( "NO\n" );
		}
	}
 
	return 0;
}