// Bolatulu
#include <bits/stdc++.h>
#include "island.h"

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
#define kanagattandirilmagandiktarinizdan ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
#define fx cout << fixed << setprecision(10);
#define file(s) freopen(s".in", "r", stdin); freopen(s".out", "w", stdout);
#define len(v) (int)v.size()
#define bitcount(n) __builtin_popcountll(n)
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define eb emplace_back
#define F first     
#define S second
#define T third
#define md (tl+tr)/2
#define TL v+v, tl,md
#define TR v+v+1, md+1,tr
#define Tl t[v].l, tl,md
#define Tr t[v].r, md+1,tr
#define yes cout << "YES\n"
#define no cout << "NO"
#define all(x) (x).begin(), (x).end()
#define cnk(n,k) mod(mod(f[(n)]*binpow(f[(n)-(k)],M-2))*binpow(f[(k)],M-2))
#define cnkf(n,k) mod(mod(f[(n)]*inv[(n)-(k)])*inv[(k)])
#define ank(n,k) mod(f[(n)]*binpow(f[(n)-(k)],M-2))
#define ankf(n,k) mod(f[(n)]*inv[(n)-(k)])
// #define int unsigned long long

#pragma GCC target( "sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")

using namespace std;

const ll INF = 1e10;
const ll HZ = 1e5;
const int MAX = INT_MAX;
const int MIN = INT_MIN;
const db pi = 3.141592653;
const int P=31;

int M = 998244353;

struct segment{int l;int r;};
struct tree{int cnt;int mn;};
struct triple{int first;int second;int third;};

bool cmpt(triple a,triple b) {
    if (a.first != b.first)
        return a.first < b.first;
    if (a.second != b.second)
        return a.second > b.second;
    return a.third < b.third;
}

bool cmps(segment a,segment b) {
    if (a.r != b.r)
        return a.r < b.r;
    return a.l > b.l;
}

ll mod(ll a,ll b=M) {
    while (a < 0)
        a += M;
    return a % b;
}

ll binpow(ll a,ll n) {
    a = mod(a);
    if (!n)
        return 1;
    if (n & 1)
        return (a * binpow(a, n - 1)) % M;
    ll x = binpow(a, n >> 1);
    return (x * x) % M;
}

const int N=1e6+7;

int n,cnt[N];
vector <int> g[N];

void construct_two_trees(int N, vector<int> U, vector<int> V) {
    n=N;
    vector<array<int, 2> > t1,t2;
    for (int i=1;i<=2*n-3;i++) {
        int u,v;
        u=U[i-1]+1, v=V[i-1]+1;
        g[u].pb(v), g[v].pb(u);
    }
    set <pair <int,int>> s;
    for (int i=1;i<=n;i++) {
        cnt[i]=g[i].size();
        s.insert({cnt[i],i});
    }
    for (int i=1;i<n-3;i++) {
        int v=s.begin()->S;
        vector <int> fs;
        for (auto now : g[v]) {
            if (cnt[now]>0) {
                s.erase({cnt[now],now});
                fs.pb(now-1);
                cnt[now]--;
                s.insert({cnt[now],now});
            }
        }
        t1.pb({v-1,fs[0]}), t2.pb({v-1,fs[1]});
        s.erase({cnt[v],v});
        cnt[v]=0;
    }
    vector <int> sd;
    for (auto now : s) {
        sd.pb(now.S-1);
        // cout <<now.S << ' ';
    }
    int v=add_vertex(sd[0],sd[1],sd[2]);
    t1.pb({sd[0],sd[1]});
    t1.pb({sd[1],sd[2]});
    t1.pb({sd[2],v});
    t2.pb({sd[2],sd[0]});
    t2.pb({v,sd[0]});
    t2.pb({v,sd[1]});
    report(t1), report(t2);
}

#ifndef ONLINE_JUDGE

void solve() {
    int n;
    cin >> n;
    vector <int> v1,u1;
    for (int i=1;i<=2*n-3;i++) {
        int x,y;
        cin >> x >> y;
        v1.pb(x), u1.pb(y);
    }
    construct_two_trees(n,v1,u1);
}

signed main() {
    // file()
    kanagattandirilmagandiktarinizdan
    fx
    int test = 1;
    // cin >> test;
    for (int i=1;i<=test;i++) { 
        // cout << "Case " << i << ": ";
        solve();
        if (i<test)
            cout << '\n';
    }
    return 0;
}

#endif