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 
#include <bits/stdc++.h>
using namespace std;
int v[1000];
int parent[1000];
int r[1000];
void make_set(int v) {
  parent[v] = v;
  r[v] = 0;
}
int find_set(int v) {
  if (parent[v] == v) {
    return v;
  }
  return parent[v] = find_set(parent[v]);
}
void make_pair(int a, int b) {
  int pa = find_set(a);
  int pb = find_set(b);
  if (r[pa] < r[pb]) {
    swap(pa, pb);
  }
  parent[pb] = pa;
  r[pa] = r[pa] + r[pb];
}
int main() {
  int t;
  cin >> t;
  int k = t;
  for (int i = 0; i < t; i++) {
    make_set(i);
  }
  int y[t], z[t];
  int counter = 0;
  t--;
  while (t--) {
    int a, b;
    cin >> a >> b;
    if (find_set(a - 1) != find_set(b - 1)) {
      make_pair(a - 1, b - 1);
    } else {
      y[counter] = a;
      z[counter] = b;
      counter++;
    }
  }
  counter--;
  if (counter == -1) {
    cout << 0;
    return 0;
  }
  for (int i = 1; i < k; i++) {
    if (find_set(i) != find_set(0)) {
      cout << y[counter] << " " << z[counter] << " " << i + 1 << " " << 1
           << endl;
      counter--;
      make_pair(i, 0);
    }
  }
  return 0;
}
