#include <iostream>
#include <fstream>
#include <cassert>
using namespace std;

ifstream fin ("euler.in");
ofstream fout("euler.out");

int n , a[205][205], d[205], x[50000], y[50000], p , q;


int main()
{
    int i , j;
    fin >> n;
    while(fin >> i >> j)
    {
        a[i][j] = a[j][i] = 1;
        d[i] ++, d[j] ++;
    }
    p = 1; x[1] = 1;
    while(1)
    {
        int xpoz = 0;
        for(int i = 1 ; i <= p && xpoz == 0 ; ++i)
            if(d[x[i]] > 0)
            xpoz = i;
            if(xpoz == 0)break;
            q = 1; y[1] = x[xpoz];
            do{
                int ypoz = 0;
                for(int i =1 ; i <= n && ypoz == 0 ; i ++)
                    if(a[y[q]][i] != 0)
                    ypoz = i;
                d[y[q]] --;
                d[ypoz] --;
                a[y[q]][ypoz] = a[ypoz][y[q]] = 0;
                y[ ++ q] = ypoz;
                }while(y[q] != y[1]);
        for(int i = p; i > xpoz ; i --)
            x[i + q - 1] = x[i];
        for(int i = xpoz, j = 1 ; j <= q ; i ++, j ++)
            x[i] = y[j];
        p += q - 1;
    }
    fout << p << "\n";
    for(int i =1 ; i <= p ; i ++)
        fout << x[i] << " ";
    return 0;
}