#include <bits/stdc++.h>
using namespace std;

#define MAXN 101

int n , m ;
int visited [MAXN] ;
int parent [MAXN] ;
set <int> different_parents ;
vector <int> adj_list [MAXN] ;
bool is_present [MAXN] ;

void dfs (int x , int *c)
{
    *c += 1 ;
    visited[x] = 1 ;

    for (int i = 0 ; i < adj_list[x].size() ; i++)
    {
        int v = adj_list[x][i] ;

        if(visited[v] == -1)
        {
            visited[v] = visited[x] ;
            dfs(v , c) ;
        }
    }
}
void dfs_print (int x)
{
    cout << x << " " ;
    visited[x] = 1 ;

    for (int i = 0 ; i < adj_list[x].size() ; i++)
    {
        int v = adj_list[x][i] ;

        if(visited[v] == -1)
        {
            visited[v] = visited[x] ;
            dfs_print(v) ;
        }
    }
}
int Find (int i)
{
    return parent[i] == i ? i : parent[i] = Find(parent[i]) ;
}
void Union (int x , int y)
{
    int xParent = Find(x) ;
    int yParent = Find(y) ;

    parent[xParent] = yParent ;
}
void initialize ()
{
    for (int i = 1 ; i <= m ; i++)
    {
        visited[i] = -1 ;
        parent[i] = i ;
    }
}
void sort_adj_list ()
{
    for (int i = 1 ; i <= m ; i++)
    {
        sort (adj_list[i].begin() , adj_list[i].end()) ;
    }
}
bool search_galaxy (int num)
{
    for (int i = 1 ; i <= m ; i++)
    {
        for (int j = 0 ; j < adj_list[i].size() ; j++)
        {
            if (adj_list[i][j] == num)
            {
                return false ;
            }
        }
    }

    return true ;
}
int main ()
{
    int a , b , v = 1 , u = INT_MIN , c = 0 ;

    cin >> n >> m ;

    initialize() ;

    for (int i = 1 ; i <= m ; i++)
    {
        parent[i] = i ;
        is_present[i] = false ;
    }

    for (int i = 1 ; i <= n ; i++)
    {
        cin >> a >> b ;

        adj_list[a].push_back(b) ;
        adj_list[b].push_back(a) ;

        Union (a , b) ;

        is_present[a] = true ;
        is_present[b] = true ;
    }

    for (int i = 1 ; i <= m ; i++)
    {
        if (is_present[i])
        {
            different_parents.insert(Find(i)) ;
        }
    }

    cout << different_parents.size() << endl ;

    sort_adj_list ();

    for (int i = 1 ; i <= m ; i++)
    {
        initialize();
        c = 0 ;
        dfs(i , &c);

        if (c > u)
        {
            u = c ;
            v = i ;
        }
    }

    initialize();
    dfs_print(v);
    cout << endl ;

    return 0;
}