#include<bits/stdc++.h>
using namespace std;
vector<int> vec[2007];
vector<int> edge;
vector<int> cp;
bool visited[2007];
void dfs(int x,int p){
if(visited[x]) return ;
visited[x]=true;
if(vec[x].size()==1 || p==-1) edge.push_back(x);
for(auto i:vec[x]){
if(i==p) continue;
if(visited[i]) continue;
dfs(i,x);
}
}
signed main(){
ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
int n; cin >> n;
for(int i=0;i<n-1;++i){
int a,b; cin >> a >> b;
vec[a].push_back(b);
vec[b].push_back(a);
}
int mn=1e9;
for(int i=1;i<=n;++i){
memset(visited,0,sizeof(visited));
edge.clear();
dfs(i,-1);
if(edge.size()<mn){
mn=edge.size();
cp=edge;
}
}
cout << cp.size()-1 << '\n';
for(int i=1;i<cp.size();++i){
cout << cp[0] << " " << cp[i] << '\n';
}
}
