#include <cmath>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <functional>
#include <queue>
#include <iostream>
#include <string.h>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <cstdint>
#include <climits>
#include <unordered_set>
#include <sstream>
#include <stack>

using namespace std;

typedef long long int ll;
typedef pair<int,int> pii;
typedef tuple<ll,ll,ll> t3;

using namespace std;
int n,m;
vector<vector<pii>> g;

vector<int> used;

int dfs(int from, int current)
{
    for(auto e : g[from])
    {
        auto index = e.second;
        if(used[index]) continue;
        auto next = e.first;
        used[index] = true;
        int count = dfs(next, current + 1);
        used[index] = false;
        if(count == m)
        {
            return m;
        }
    }
    return current;
}


bool dfs()
{
    int index = -1;
    int valid = -1;
    for(int i = 0;i < n;i++)
    {
        if(g[i].size() == 1)
        {
            index = i;
            break;
        }
        else if(g[i].size() > 1)
        {
            valid = i;
        }
    }
    if(index >= 0)
    {
        int to = g[index][0].first;
        used[g[index][0].second] = true;
        int r = dfs(to, 1);
        if(r == m)
        {
            return true;
        }
        return false;
    }
    else
    {
        int to = g[valid][0].first;
        used[g[valid][0].second] = true;
        int r = dfs(to, 1);
        if(r == m)
        {
            return true;
        }
        return false;
    }
}

int main()
{
    cin >> n >> m;
    g.resize(n);
    used.assign(m, 0);
    for(int i = 0;i < m;i++)
    {
        int a, b;
        cin >> a >> b;
        g[a].emplace_back(b,i);
        g[b].emplace_back(a,i);
    }
    
    if(dfs())
    {
        cout << "YES" << endl;
        return 0;
    }
    cout << "NO" << endl;
    return 0;
}