#include <bits/stdc++.h>
#define nmax 101
using namespace std;
ifstream fin("lant1.in");
ofstream fout("lant1.out");
int a[nmax][nmax],p,q,n,x,y,nsol,r;
vector<int>h[nmax];
queue<int>c;
int viz[nmax],sol[nmax],refacere[nmax];
void Citire()
{
    fin>>n>>p>>q>>r;
    while(fin>>x>>y)
    {
        h[x].push_back(y);
        h[y].push_back(x);
    }
}
void BFS(int t)
{
    int x,i;
    viz[t]=1;
    c.push(t);
    while(!c.empty())
    {
        x=c.front();
        c.pop();
        for(i=0;i<h[x].size();i++)
            if(!viz[h[x][i]])
        {
            viz[h[x][i]]=1;
            sol[h[x][i]]=x;
            c.push(h[x][i]);
        }
    }
}
void Drum(int x)
{
    if(x==r)
        return;
    Drum(sol[x]);
    refacere[++nsol]=x;
}
void Drum1(int x)
{
    if(x==p)
    {
        refacere[++nsol]=x;
        return;
    }
    Drum1(sol[x]);
    refacere[++nsol]=x;
}
int main()
{
    int i;
    Citire();
    BFS(p);
    Drum1(r);
    for(i=1;i<=nmax;i++)
        sol[i]=viz[i]=0;
    BFS(r);
    Drum(q);
    fout<<nsol<<"\n";
    for(i=1;i<=nsol;i++)
        fout<<refacere[i]<<" ";
    fin.close();
    fout.close();
    return 0;
}