#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define dd(x) cout<<#x<<" is "<<x<<endl;
#define dd2(x,y) cout<<#x<<" is "<<x<<" "<<#y<<" is "<<y<<endl;
#define dl(x) cout<<#x<<" is "<<endl; for(int i=1; i<9; i++) cout<<x[i]<<' '; cout<<endl;
#define fi first
#define se second
typedef pair<int,int> pii;
const int N = 11;
vector<int>adj[N];
int p[N], r[N];
int fs(int x){
if(p[x] == x) return x;
else return p[x] = fs(p[x]);
}
void merge(int a, int b){
a = fs(a), b = fs(b);
if(r[a] < r[b]) swap(a,b);
p[b] = a;
if(r[a] == r[b]) r[a]++;
}
vector<pii>edges;
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
int n; cin>>n;
for(int i=0; i<n-1; i++){
int a,b; cin>>a>>b;
adj[a].pb(b);
adj[b].pb(a);
edges.pb({a,b});
}
vector<int>leaves;
for(int i=1; i<=n; i++){
if(adj[i].size() == 1) leaves.pb(i);
}
vector<int>v;
for(int i=1; i<=n; i++) v.pb(i);
int ans = LLONG_MAX;
vector<int>save;
do{
bool f = 0;
int cnt = 0;
for(int e=0; e<n-1; e++){ //edge to not take
int cc = 0;
for(int i=1; i<=n; i++) p[i] = i, r[i] = 0;
for(int i=0; i<leaves.size(); i++){
int u = leaves[i];
int c = v[i];
if(fs(u) == fs(c)) continue;
cc++;
merge(u,c);
}
cnt = cc;
for(int j=0; j<n-1; j++){
if(j == e) continue;
merge(edges[j].fi, edges[j].se);
}
if(fs(edges[e].fi) != fs(edges[e].se)) {f=1; break;}
}
if(f == 0 and cnt < ans){
ans = cnt;
save = v;
}
} while(next_permutation(v.begin(), v.end()));
cout<<ans<<'\n';
for(int i=1; i<=n; i++) p[i] = i, r[i] = 0;
for(int i=0; i<leaves.size(); i++){
int u = leaves[i];
int c = save[i];
if(fs(u) == fs(c)) continue;
merge(u,c);
cout<<u<<' '<<c<<'\n';
}
return 0;
}
