/*
DEATH-MATCH
Davit-Marg
*/
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <cstring>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <iterator>
#include <ctype.h>
#include <stdlib.h>  
#include <cassert>
#include <fstream>  
#define mod 1000000007ll
#define LL long long
#define LD long double
#define MP make_pair
#define PB push_back
using namespace std;
ifstream fin("maxpath.in");
ofstream fout("maxpath.out");

int n, m, used[500005];
vector<LL> g[500005];
vector<int> v, best, a;
LL sum, bsum;

void dfs(LL k, LL d = 1)
{
	used[k] = 1;
	sum += d * k;
	v.PB(k);

	random_shuffle(g[k].begin(), g[k].end());
	for (int i = 0; i < g[k].size(); i++)
	{
		int to = g[k][i];
		if (used[to])
			continue;
		dfs(to, d + 1);
	}


	if (sum > bsum)
	{
		bsum = sum;
		best = v;
	}
	sum -= d * k;
	v.pop_back();
}

void bfs(int k, int st = 1)
{
	used[k] = 1;
	//random_shuffle(g[k].begin(), g[k].end());
	vector<int> a[2];
	queue<pair<int, int>> q;
	q.push(MP(g[k][0], 0));
	q.push(MP(g[k][1], 1));
	while (!q.empty())
	{
		pair<int, int> now = q.front();
		q.pop();
		if (used[now.first])
			continue;
		a[now.second].PB(now.first);
		used[now.first] = 1;
		for (int i = 0; i < g[now.first].size(); i++)
		{
			int to = g[now.first][i];
			if (used[to])
				continue;
			q.push(MP(to, now.second));
			break;
		}
	}
	reverse(a[0].begin(), a[0].end());
	for (int i = 0; i < a[0].size(); i++)
	{
		v.PB(a[0][i]);
		sum += (LL)v.size()*(LL)v.back();
	}
	v.PB(k);
	sum += (LL)v.size()*(LL)v.back();
	for (int i = 0; i < a[1].size(); i++)
	{
		v.PB(a[1][i]);
		sum += (LL)v.size()*(LL)v.back();
	}

	if (sum > bsum)
	{
		bsum = sum;
		best = v;
	}
	sum = 0;
	v.resize(0);
}

int main()
{
	fin >> n >> m;
	bsum = n;
	best.PB(n);

	for (int i = 0; i < m; i++)
	{
		int a, b;
		fin >> a >> b;
		g[a].PB(b);
		g[b].PB(a);
	}

	if (n <= 1000)
	{
		m += n;
		m /= 2;
		if (m == 0)
			m++;
		for (int i = 1; i <= n && a.size()<200; i++)
			if (g[i].size() == 1)
				a.PB(i);

		while ((int)a.size() < 20000000 / m)
			a.PB(n - (rand() % (n / 6)));

		while ((int)a.size() < 25000000 / m)
			a.PB(rand() % n + 1);

		random_shuffle(a.begin(), a.end());
		for (int i = 0; i < min((int)a.size(), 25000000 / m); i++)
		{
			memset(used, 0, (n + 2) * sizeof(int));
			if (g[a[i]].size() == 1 || n <= 1000)
				dfs(a[i]);
			else if (g[a[i]].size() >= 2)
				bfs(a[i], 1);
		}
		fout << best.size() << endl;
		for (int i = 0; i < best.size(); i++)
			fout << best[i] << " ";
		fout << endl;
		return 0;
	}

	for (int i = 1; i <= n; i++)
		if (g[i].size() == 1)
			a.PB(i);

	while ((int)a.size() < 20000000 / (m + n))
		a.PB(n - (rand() % (n / 6)));

	while ((int)a.size() < 25000000 / (m + n))
		a.PB(rand() % n + 1);

	random_shuffle(a.begin(), a.end());
	for (int i = 0; i < min((int)a.size(), 25000000 / (m + n)); i++)
	{
		memset(used, 0, (n + 2) * sizeof(int));
		if (g[a[i]].size() == 1 || n <= 1000)
			dfs(a[i]);
		else if (g[a[i]].size() >= 2)
			bfs(a[i], 1);
	}
	fout << best.size() << endl;
	for (int i = 0; i < best.size(); i++)
		fout << best[i] << " ";
	fout << endl;
	return 0;
}

/*

5 3
4 5
5 1
1 4


5 5
1 2
2 3
2 5
2 4
3 5

*/