#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;
int visit[MAX];

void dfs(int v, int p, int d, const vector<vi>& G) {
    visit[v] |= 1<<d;
    if (d == 2) {
        return;
    }
    for (int ch : G[v]) {
        if (ch != p && (visit[ch]>>(d+1) == 0)) {
            dfs(ch, v, d+1, G);
        }
    }
}

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);
    }
    dfs(0, -1, 0, G);
    for (int i = 1; i < N; i++) {
        for (int ch : G[i]) {
            if (visit[i] >= 4 && visit[ch] >= 4) {
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}