#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <queue>
#include <algorithm>
#include <fstream>
#include <functional>
#include <climits>
#include <cmath>

using namespace std;

#define mp(first, second) make_pair(first, second)

typedef unsigned long long ul;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<int> vi;

int n, m;
vector<vi> graph;
vi visited;
vi dist;
vi previous;

void bfs(int start) {
	visited.assign(n, false);
	dist.assign(n, INT_MAX);
	previous.assign(n, -1);
	queue<int> q;
	q.push(start);
	dist[start] = 0;

	while (!q.empty())
	{
		int curr = q.front();
		q.pop();

		if (!visited[curr])
		{
			visited[curr] = true;
			for (int i = 0; i < graph[curr].size(); i++) {
				int u = graph[curr][i];

				if (!visited[u])
				{
					dist[u] = dist[curr] + 1;
					q.push(u);
					previous[u] = curr;
				}
			}
		}
	}
}

int main() {
	ios_base::sync_with_stdio(false);

	ifstream cin("maxpath.in");
	ofstream cout("maxpath.out");

	cin >> n >> m;
	graph.resize(n);

	for (int i = 0; i < m; i++) {
		int u, v; cin >> u >> v;
		--u; --v;

		graph[u].push_back(v);
		graph[v].push_back(u);
	}

	int bestDist = INT_MIN;
	int startNode = -1;
	vi retrace;
	for (int i = 0; i < min(n, 1000); i++) {
		bfs(i);

		/*cout << "after " << i << endl;
		for (int i = 0; i < n; i++) {
			cout << dist[i] << " ";
		}
		cout << endl;*/

		bool shouldRetrace = false;
		for (int j = 0; j < n; j++) {
			if (dist[j] > bestDist)
			{
				bestDist = dist[j];
				startNode = j;
				shouldRetrace = true;
			}
		}

		if (shouldRetrace)
		{
			retrace.clear();
			while (startNode != -1)
			{
				retrace.push_back(startNode + 1);
				startNode = previous[startNode];
			}
		}
	}

	cout << retrace.size() << endl;
	for (int i = 0; i < retrace.size(); i++) {
		cout << retrace[i] << endl;
	}
 
	//while (true)
	//{

	//}

	return 0;
}