#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M;
    vector<vector<P>> graph(N);
    for(int i = 0; i < M; ++i){
        int u, v;
        cin >> u >> v;
        graph[u].emplace_back(v, i);
        graph[v].emplace_back(u, i);
    }

    for(int s = 0; s < N; ++s){
        auto g = graph;
        int cnt = 0;
        vector<bool> used(M);
        queue<int> que;
        int v = s;
        bool update = true;
        while(update){
            update = false;
            int n = g[v].size();
            for(int i = n - 1; i >= 0; --i){
                auto [u, j] = graph[v][i];
                if(used[j]) g[v].pop_back();
                else{
                    cnt += 1;
                    used[j] = true;
                    g[v].pop_back();
                    v = u;
                    update = true;
                    break;
                }
            }
        }
        if(cnt == M){
            cout << "YES\n";
            return 0;
        }
    }
    cout << "NO\n";

    return 0;
}