简单的dfs从1节点开始往下深搜，然后回溯记录路径
#include<bits/stdc++.h>
using namespace std;
const int N=1e4+10;
vector<int>a[N];
int n,m;
vector<int>p;
void dfs(int x,int y){
if(x==m){
cout<<p.size()<<"\n";
for(auto c:p){
cout<<c<<" ";
}
return;
}
for(auto c:a[x]){
if(c==y)continue;
p.push_back(c);
dfs(c,x);
p.pop_back();
}
}
int main(){
cin>>n>>m;
for(int i=1;i<=n-1;i++){
int u,v;
cin>>u>>v;
a[u].push_back(v);
a[v].push_back(u);
}
p.push_back(1);
dfs(1,0);
return 0;
}