#include <iostream>
#include <vector>
#include <set>
using namespace std;
const int N=20000;
vector<int> edge[N];
set<int> list[N];
void dfs(int cur,int parent,int state){
	if(state==2){
		list[cur].insert(parent);
		return;
	}
	for(int i=0;i<edge[cur].size();i++){
		if(parent==edge[cur][i])	continue;
		dfs(edge[cur][i],cur,state+1);
	}
	return;
}
int main(){
	int n,m;	cin>>n>>m;
	vector<int> a(m),b(m);
	for(int i=0;i<m;i++){
		cin>>a[i]>>b[i];	a[i]--;	b[i]--;
		edge[a[i]].push_back(b[i]);
		edge[b[i]].push_back(a[i]);
	}
	dfs(0,0,0);
	for(int i=0;i<m;i++){
		bool flaga=false,flagb=false;
		if(list[b[i]].find(a[i])!=list[b[i]].end()){
			flaga=true;
			list[b[i]].erase(a[i]);
		}
		if(list[a[i]].find(b[i])!=list[a[i]].end()){
			flagb=true;
			list[a[i]].erase(b[i]);
		}
		int numa=list[a[i]].size();
		int numb=list[b[i]].size();
		if(numa==0||numb==0||(numa==1&&numb==1&&*list[a[i]].begin()==*list[b[i]].begin())){
			if(flaga)	list[b[i]].insert(a[i]);
			if(flagb)	list[a[i]].insert(b[i]);
			continue;
		}
		cout<<"YES"<<endl;
		return 0;
	}
	cout<<"NO"<<endl;
	return 0;
}