#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

int n,m;
vector<bool> g[25252];
short deg[25252];
int es[52525];
#define SHIFT 16
#define MASK 65535

int main(){
  scanf("%d%d",&n,&m);
  REP(i,n)g[i].assign(n,false);
  REP(i,m){
    int a,b;
    scanf("%d%d",&a,&b);--a;--b;
    g[a][b] = g[b][a] = true;
    es[i] = (a<<SHIFT)+b;
    deg[a]+=1;
    deg[b]+=1;
  }
  bool flag = false;
  REP(i,m){
    int a,b,c,d;
    a = es[i]>>SHIFT;
    b = es[i]&MASK;
    if(a==0 || b==0)continue;
    if(deg[a]==1 || deg[b]==1)continue;
    if(!g[a][0] && !g[b][0])continue;
    REP(j,i){
      c = es[j]>>SHIFT;
      d = es[j]&MASK;
      if(c==0 || d==0 || a==c || a==d || b==c || b==d)continue;
      if(deg[c]==1 || deg[d]==1)continue;
      if(!g[c][0] && !g[d][0])continue;
      if(g[a][0]){
        if(g[b][c] && g[d][0]){
          flag = true;
          break;
        }else if(g[b][d] && g[c][0]){
          flag = true;
          break;
        }
      }
      if(g[b][0]){
        if(g[a][c] && g[d][0]){
          flag = true;
          break;
        }else if(g[a][d] && g[c][0]){
          flag = true;
          break;
        }
      }
    }
    if(flag)break;
  }
  puts(flag?"YES":"NO");
  return 0;
}