#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <iomanip>
#include <cassert>
using namespace std;

#define GET_ARG(a,b,c,F,...) F
#define REP3(i,s,e) for (i = s; i <= e; i++)
#define REP2(i,n) REP3 (i,0,(int)(n)-1)
#define REP(...) GET_ARG (__VA_ARGS__,REP3,REP2) (__VA_ARGS__)
#define RREP3(i,s,e) for (i = s; i >= e; i--)
#define RREP2(i,n) RREP3 (i,(int)(n)-1,0)
#define RREP(...) GET_ARG (__VA_ARGS__,RREP3,RREP2) (__VA_ARGS__)
#define DEBUG(x) cerr << #x ": " << x << endl

vector<int> e[20000];
bool used[20000];

bool dfs(int v, int d) {
    bool ret = false;
    used[v] = true;
    for (auto x: e[v]) {
        if (x == 0 && d == 4) ret = true;
        if (!used[x] && d < 4) ret |= dfs(x,d+1);
    }
    used[v] = false;
    return ret;
}

int main(void) {
    int i, n, m;
    scanf("%d%d",&n,&m);
    REP (i,m) {
        int a, b;
        scanf("%d%d",&a,&b);
        a--; b--;
        e[a].push_back(b);
        e[b].push_back(a);
    }
    if (dfs(0,0))
        puts("YES");
    else
        puts("NO");
    return 0;
}