#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<stack>
#include<queue>
#include<vector>
#include<algorithm>
#include<string>
#include<iostream>
#include<set>
#include<map>
#include<bitset>

using namespace std;
typedef long long ll;
#define i_7 (ll)(1E9+7)
#define i_5 (ll)(1E9+5)
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    else return c+i_7;
}
typedef pair<int,int> i_i;
typedef pair<ll,ll> l_l;
ll inf=(ll)1E12;/*10^12*/
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}

////////////////////////////////////////

bool check(vector<int>v,vector<int>u){
    sort(v.begin(),v.end());
    v.erase(unique(v.begin(),v.end()),v.end());
    sort(u.begin(),u.end());
    u.erase(unique(u.begin(),u.end()),u.end());
    
    set<int>s;
    ll vv=v.size(),uu=u.size();
    for(auto x:v)s.insert(x);
    for(auto x:u)s.insert(x);
    ll ss=s.size();
    return ss==vv+uu;
}

int main(){
    int n,m;cin>>n>>m;
    vector<int>v[n];
    rep(i,0,m-1){
        int s,t;cin>>s>>t;s--;t--;
        v[s].pb(t);
        v[t].pb(s);
    }
    vector<int>v0,v1,v2;
    for(auto x:v[0])v0.pb(x);
    for(auto x:v0){
        for(auto y:v[x])v1.pb(y);
    }
    sort(v1.begin(),v1.end());
    v1.erase(unique(v1.begin(),v1.end()),v1.end());
    for(auto x:v1){
        for(auto y:v[x])v2.pb(y);
    }
    
    if(!check(v1,v2)){
        cout<<"YES"<<endl;
    }else{
        cout<<"NO"<<endl;
    }
    
    return 0;
}