#include<bits/stdc++.h>
using namespace std;

#define int long long
#define ii pair<int, int>
#define fi first
#define se second
const int maxn = 3e6 + 25;
const int mod = 1e9 + 7;
const int oo = 1e16 + 7;

#define all(x) x.begin(), x.end()

int dx[] = {0, 1, -1, 0};
int dy[] = {1, 0, 0, -1};

int n, m;
bitset<2003> adj[1005];


void solve()
{
    cin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int u, v; cin>> u >> v;
        adj[u].set(v, 1);

        adj[v].set(u, 1);
    }
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            if(i == j) continue;
            if((adj[i] & adj[j]).count() < 3) continue;
            for(int k = 1; k <= n; k++)
            {
                if(k == j || k == i) continue;

                if((adj[i] & adj[j] & adj[k]).count() >= 3)
                {
                    cout << "YES\n";
                    return ;
                }
            }
        }
    }
    cout << "NO\n";
}


int32_t main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if(fopen("main.inp", "r"))
    {
        freopen("main.inp", "r", stdin);
//        freopen("main.out", "w", stdout);
    }
    int test = 1;
//    cin >> test;
    while(test--) solve();
}