#include <iostream>
#include <vector>
#include <set>
#include <cassert>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
using namespace std;
int main() {
    int n, m; cin >> n >> m;
    vector<vector<int> > g(n);
    repeat (i,m) {
        int a, b; cin >> a >> b; -- a; -- b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    const int root = 0;
    set<int> d1; for (int i : g[root]) d1.insert(i);
    set<int> d2; for (int i : g[root]) for (int j : g[i]) if (j != root) d2.insert(j);
    vector<vector<int> > g1(n); repeat (i,n) for (int j : g[i]) if (d1.count(j)) g1[i].push_back(j);
    bool ans = false;
    for (int i : d2) for (int j : d2) if (i < j) {
        assert (not g1[i].empty());
        assert (not g1[j].empty());
        if (g1[i].size() == 1 and g1[j].size() == 1 and g1[i][0] == g1[j][0]) continue;
        ans = true;
        goto done;
    }
done:
    cout << (ans ? "YES" : "NO") << endl;
    return 0;
}