#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=50010;
int n,root,tot,son[N],fa[N],top[N],size[N],dep[N],id[N],rk[N],head[N];
bool flag[N];
struct edge
{
	int next,to;
}e[N*2];
struct Treenode
{
	int l,r,maxn,pos,lazy;
};
struct Tree
{
	Treenode tree[N*4];
	int tot;
	void pushup(int x)
	{
		if (tree[x*2].maxn>tree[x*2+1].maxn)
		{
			tree[x].maxn=tree[x*2].maxn;
			tree[x].pos=tree[x*2].pos;
		}
		else if (tree[x*2].maxn<tree[x*2+1].maxn)
		{
			tree[x].maxn=tree[x*2+1].maxn;
			tree[x].pos=tree[x*2+1].pos;
		}
		else if (tree[x*2].maxn==tree[x*2+1].maxn&&tree[x*2].pos<tree[x*2+1].pos)
		{
			tree[x].maxn=tree[x*2].maxn;
			tree[x].pos=tree[x*2].pos;
		}
		else
		{
			tree[x].maxn=tree[x*2+1].maxn;
			tree[x].pos=tree[x*2+1].pos;
		}
	}
	void pushdown(int x)
	{
		if (tree[x].lazy)
		{
			tree[x*2].lazy+=tree[x].lazy;
			tree[x*2+1].lazy+=tree[x].lazy;
			tree[x*2].maxn+=tree[x].lazy;
			tree[x*2+1].maxn+=tree[x].lazy;
			tree[x].lazy=0;
		}
	}
	void build(int x,int l,int r)
	{
		tree[x].l=l; tree[x].r=r;
		if (l==r)
		{
			tree[x].maxn=dep[rk[l]];
			tree[x].pos=rk[l];
			return;
		}
		int mid=(l+r)>>1;
		build(x*2,l,mid); build(x*2+1,mid+1,r);
		pushup(x);
	}
	void update(int x,int l,int r)
	{
		if (tree[x].l==l && tree[x].r==r)
		{
			tree[x].lazy--;
			tree[x].maxn--;
			return;
		}
		pushdown(x);
		int mid=(tree[x].l+tree[x].r)>>1;
		if (r<=mid) update(x*2,l,r);
		else if (l>mid) update(x*2+1,l,r);
		else update(x*2,l,mid),update(x*2+1,mid+1,r);
		pushup(x);
	}
}Tree;
void add(int from,int to)
{
	e[++tot].to=to;
	e[tot].next=head[from];
	head[from]=tot;
}
void dfs1(int x,int f)
{
	dep[x]=dep[f]+1;
	size[x]=1; 
	fa[x]=f;
	for (int i=head[x];~i;i=e[i].next)
	{
		int v=e[i].to;
		if (v!=f)
		{
			dfs1(v,x);
			size[x]+=size[v];
			if (size[v]>size[son[x]]) son[x]=v;
		}
	}
}
void dfs2(int x,int tp)
{
	top[x]=tp; 
	id[x]=++tot; 
	rk[tot]=x;
	for (int i=head[x];~i;i=e[i].next)
	{
		if(e[i].to==son[x]) dfs2(e[i].to,tp);
	}
	for (int i=head[x];~i;i=e[i].next)
	{
		int v=e[i].to;
		if (v!=son[x] && v!=fa[x]) dfs2(v,v);
	}
}

int main()
{
	freopen("apple.in","r",stdin);
    freopen("apple.out","w",stdout);
	memset(head,-1,sizeof(head));
	scanf("%d%d",&n,&root);
	root++;
	for (int i=1;i<n;i++)
	{
		int x,y;
		scanf("%d%d",&x,&y);
		add(x+1,y+1);
		add(y+1,x+1);
	}
	dep[0]=-1; 
	tot=0;
	dfs1(root,0); 
	dfs2(root,root);
	Tree.build(1,1,n);
	printf("%d\n",root-1);
	flag[root]=1;
	while (Tree.tree[1].maxn)
	{
		int pos=Tree.tree[1].pos;
		printf("%d\n",pos-1);
		for(;!flag[pos];pos=fa[pos])
		{
			Tree.update(1,id[pos],id[pos]+size[pos]-1);
			flag[pos]=1;
		}
	}
	return 0;
}