#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
//#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
//#include<list>
#include<queue>
#include<deque>
#include<algorithm>
//#include<numeric>
#include<utility>
//#include<memory>
#include<functional>
#include<cassert>
#include<set>
#include<stack>
#include<random>

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, -1, 0, 1};
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

const int MAX = 20020;
vector<int> from[MAX];

void check(int v, const vector<vi>& G) {
    for (int ch : G[v]) if (ch != 0) {
        if (from[ch].size() < 3) from[ch].push_back(v);
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, M;
    cin >> N >> M;
    vector<vector<int> > G(N);
    for (int i = 0; i < M; i++) {
        int a, b;
        cin >> a >> b;
        a--; b--;
        G[a].emplace_back(b);
        G[b].emplace_back(a);
    }
    for (int v : G[0]) {
        check(v, G);
    }
    for (int i = 1; i < N; i++) {
        for (int ch : G[i]) {
            for (int j = 0; j < from[i].size(); j++) for (int k = 0; k < from[ch].size(); k++) {
                if (from[i][j] != ch && from[i][j] != from[ch][k] && from[ch][k] != i) {
                    cout << "YES" << endl;
                    return 0;
                }
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}