fn.cpp
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<math.h>
#include<vector>
using namespace std;
#define FOR(i,a,b) for(int i=a; i<=b; i++)
#define PII pair<int, int>
#define MP make_pair
#define PB push_back
#define SIZE(s) (int)(s).int()
#define ll long long
#define MAX 10047
int V[MAX];
int N, M;
int main()
{
int a, b;
while(scanf("%d %d",&N, &M)== 2)
{
FOR(i,0,N-1) V[i] = 0;
while(M--)
{
scanf("%d %d",&a,&b);
a--; b--;
V[a]++;
V[b]++;
}
bool ok = false;
FOR(i,0,N-1)
{
if (V[i] >= 4) ok = true;
}
if (ok) puts("YES");
else puts("NO");
}
return 0;
}