4
1 4
3 1
3 4
 5
4 1
4 3
5 3
2 4
 21
7 15
13 1
14 3
4 10
2 3
16 18
17 20
16 20
8 4
3 12
2 17
13 11
16 1
13 2
13 5
8 9
6 14
3 17
16 9
13 8
 3
3 1
3 2
 6
5 2
5 3
1 4
3 1
5 6
 60
17 34
46 22
50 44
46 33
41 21
31 33
48 6
38 19
35 60
2 24
49 29
7 53
34 1
19 55
32 1
31 42
27 28
4 53
6 50
21 34
1 10
12 36
54 8
16 13
51 43
45 51
54 20
13 53
34 33
49 33
51 11
59 34
15 5
59 28
30 39
13 30
58 4
34 14
3 9
19 34
4 18
26 48
56 54
3 43
57 25
3 41
35 3
48 44
19 13
54 1
23 31
59 47
5 1
46 40
6 26
20 25
37 5
17 24
20 52
 3
3 2
1 2
 39
6 13
15 39
10 35
31 28
4 21
12 39
3 7
3 13
6 1
5 14
36 28
12 15
18 38
30 29
19 34
36 16
20 22
8 13
38 32
26 39
21 37
1 7
15 27
12 26
8 3
6 14
29 2
25 23
32 21
5 16
32 25
6 8
13 10
23 30
34 37
29 33
28 14
36 5
 10
5 9
8 5
7 6
7 9
3 9
2 1
7 2
3 6
7 1

1
3 4 1 2  0
 3
13 2 1 7 3 17 1 19 13 8 1 21  0
 0
 2
48 44 1 6 6 26 1 12  0
 7
12 15 1 2 1 7 1 9 12 26 1 11 8 3 1 12 6 8 1 17 28 14 1 20 36 5 1 24  2
3 6 1 4 7 1 1 10 
// the212guy
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
 
#define ff              first
#define ss              second
#define int             long long
#define pb              push_back
#define mp              make_pair
#define pii             pair<int,int>
#define vi              vector<int>
#define mii             map<int,int>
#define pqb             priority_queue<int>
#define pqs             priority_queue<int,vi,greater<int> >
#define setbits(x)      __builtin_popcountll(x)
#define zrobits(x)      __builtin_ctzll(x)
#define mod             1000000007
#define inf             1e18
#define ps(x,y)         fixed<<setprecision(y)<<x
#define mk(arr,n,type)  type *arr=new type[n];
#define w(x)            int x; cin>>x; while(x--)
mt19937                 rng(chrono::steady_clock::now().time_since_epoch().count());
 
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
 int p[1005];
 int sz[1005];
 int parent(int i){
 	if(p[i]<0)
 		return i;
 	return p[i]=parent(p[i]);
 }
 bool join(int i,int j){
     int u=parent(i),v=parent(j);
       if(u==v)
     	  return 0;

       if(sz[u]>sz[v]){
       	   p[v]=u;
       	   sz[u]+=sz[v];
       }else{
       	  p[u]=v;
       	  sz[v]+=sz[u];
       }
       return 1;

 }

 
int32_t main()
{
   ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifndef ONLINE_JUDGE
    freopen("../input.txt", "r", stdin);
    freopen("../output.txt", "w", stdout);
#endif
      vector<pii> gr;
      int  n,a,b;
      cin>>n;
      memset(p,-1,sizeof(p));
      memset(sz,1,sizeof(sz));
      for(int i=1;i<n;i++){
      	cin>>a>>b;
      	  if(!join(a,b))
      	  	gr.pb({a,b});
      }
      vi suv;
      for(int i=1;i<=n;i++)
      	  if(p[i]<0)
      	  	 suv.pb(i);

      if(gr.empty())
      	  cout<<0;
      else{
      	for(int i=0;i<gr.size();i++)
      		cout<<gr[i].ff<<" "<<gr[i].ss<<" "<<suv[i]<<" "<<suv[i+1]<<"\n";
      }	

   // 	You have submitted exactly the same code before

   int x=2+2;

    return 0;
}
