#include <fstream>

//test pentru matrice

using namespace std;

ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");

int v[100001][100001], n, nod[40001], p;

void citire()
{
    int x, y;
    in>>n;
    while(in>>x>>y)
        v[x][y]=v[y][x]=1;
}

void dfs(int x)
{
    for(int i=1; i<=n; i++)
    {
        if(v[x][i]==1)
        {
            v[x][i]=v[i][x]=0;
            dfs(i);
            nod[++p]=i;
        }
    }
}

void afisare()
{
    nod[++p]=1;
    out<<p<<'\n';
    for(int i=1; i<=p; i++)
        out<<nod[i]<<" ";
}

int main()
{
    citire();
    dfs(1);
    afisare();
    return 0;
}