#include <fstream>

using namespace std;
ifstream f ("lant1.in");
ofstream g ("lant1.out");
int n,p,l,pr,u,q,r,x,y,nr,i,c[101],viz[101],t[101],a[101][101];
void lant (int x)
{if (t[x])
{lant(t[x]);
g<<x<<" ";
}
}
int main()
{f>>n>>p>>q>>r;
while (f>>x>>y)
{
a[x][y]=a[y][x]=1;
}
pr=1;
u=1;
c[pr]=r;
viz[r]=1;
t[r]=0;
while (pr<=u)
{x=c[pr];
++pr;
for (i=1;i<=n;++i)
    if (a[i][x]==1&&viz[i]==0)
{++u;
c[u]=i;
viz[i]=viz[x]+1;
t[i]=x;
}
}
g<<viz[q]+viz[p]-1<<'\n';
x=p;
while (x!=0)
{g<<x<<" ";
x=t[x];
}
lant(q);
return 0;
}