#include <bits/stdc++.h>
using namespace std;
const int MAXN = 5e5+5;
vector<int> adj[MAXN];
vector<int> deg,leaf;
void dfs(int u, int p){
if(deg[u] == 1){
leaf.push_back(u);
return;
}
for(auto v : adj[u]){
if(v != p){
dfs(v,u);
}
}
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N; cin >> N;
deg = vector<int>(N+1,0);
for(int i = 0;i<=N-2;++i){
int u,v; cin >> u >> v;
adj[u].push_back(v); adj[v].push_back(u);
++deg[u]; ++deg[v];
}
int root = 1;
for(int i = 1;i<=N;++i){
if(deg[i] >= 2){
root = i;
}
}
dfs(root,0);
int cnt = leaf.size()/2;
if(leaf.size() % 2 == 1) ++cnt;
for(int i = 0;i<=(leaf.size()/2)-1;++i){
cout << leaf[i] << " " << leaf[i+leaf.size()/2] << "\n";
}
if(leaf.size() % 2 == 1){
cout << leaf[0] << " " << leaf.back() << "\n";
}
return 0;
}
