#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <cassert>
#include <climits>
#include <numeric>
#include <functional>
#include <time.h>
#include <bitset>
#include <emmintrin.h>

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> Pii;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, a, b) for (int i = (int)a; i <= (int)b; i++)
template<class T> void checkmin(T &a, T b) { if (b < a) a = b; }
template<class T> void checkmax(T &a, T b) { if (b > a) a = b; }

const int MaxN = 20000;
const int MaxM = 50000;
int N, M;
ll Adj[MaxN][(MaxN + 63) / 64];
Pii E[MaxM];

void solve() {
    rep(ea, M) {
        int a = E[ea].first, b = E[ea].second;
        bool adjA = Adj[0][a >> 6] >> (a & 63) & 1;
        bool adjB = Adj[0][b >> 6] >> (b & 63) & 1;
        if (!adjA && !adjB) continue;
        ll eb = lower_bound(E + ea + 1, E + M, Pii(a + 1, 0)) - E;
        for (; eb < M; eb++) if (E[eb].first != b && E[eb].second != b) {
            int c = E[eb].first, d = E[eb].second;
            if (Adj[0][c >> 6] >> (c & 63) & 1) {
                if (adjA && Adj[b][d >> 6] >> (d & 63) & 1 || adjB && Adj[a][d >> 6] >> (d & 63) & 1) {
                    cout << "YES\n";
                    return;
                }
            }
            if (Adj[0][d >> 6] >> (d & 63) & 1) {
                if (adjA && Adj[b][c >> 6] >> (c & 63) & 1 || adjB && Adj[a][c >> 6] >> (c & 63) & 1) {
                    cout << "YES\n";
                    return;
                }
            }
        }
    }
    cout << "NO\n";
}

int main() {
    scanf("%d %d", &N, &M);
    int mi = 0;
    rep(i, M) {
        int a, b;
        scanf("%d %d", &a, &b);
        a--; b--;
        Adj[a][b >> 6] |= 1LL << (b & 63);
        Adj[b][a >> 6] |= 1LL << (a & 63);
        if (a > b) swap(a, b);
        if (a != 0) E[mi++] = Pii(a, b);
    }
    M = mi;
    sort(E, E + M);
    solve();
    return 0;
}