description: This is the easy version of the problem. The only difference between the two versions is the constraint on n. You can make hacks only if all versions of the problem are solved.
  
  A forest is an undirected graph without cycles (not necessarily connected).
  
  Mocha and Diana are friends in Zhijiang, both of them have a forest with nodes numbered from 1 to n, and they would like to add edges to their forests such that: 
  
    * After adding edges, both of their graphs are still forests. 
    * They add the same edges. That is, if an edge (u, v) is added to Mocha's forest, then an edge (u, v) is added to Diana's forest, and vice versa. 
  
  
  
  Mocha and Diana want to know the maximum number of edges they can add, and which edges to add.
  
  Input
  
  The first line contains three integers n, m_1 and m_2 (1 ≤ n ≤ 1000, 0 ≤ m_1, m_2 < n) — the number of nodes and the number of initial edges in Mocha's forest and Diana's forest.
  
  Each of the next m_1 lines contains two integers u and v (1 ≤ u, v ≤ n, u ≠ v) — the edges in Mocha's forest.
  
  Each of the next m_2 lines contains two integers u and v (1 ≤ u, v ≤ n, u ≠ v) — the edges in Diana's forest.
  
  Output
  
  The first line contains only one integer h, the maximum number of edges Mocha and Diana can add (in each forest).
  
  Each of the next h lines contains two integers u and v (1 ≤ u, v ≤ n, u ≠ v) — the edge you add each time.
  
  If there are multiple correct answers, you can print any one of them.
  
  Examples
  
  Input
  
  
  3 2 2
  1 2
  2 3
  1 2
  1 3
  
  
  Output
  
  
  0
  
  
  Input
  
  
  5 3 2
  5 4
  2 1
  4 3
  4 3
  1 4
  
  
  Output
  
  
  1
  2 4
  
  
  Input
  
  
  8 1 2
  1 7
  2 6
  1 5
  
  
  Output
  
  
  5
  5 2
  2 3
  3 4
  4 7
  6 8
  
  Note
  
  In the first example, we cannot add any edge.
  
  In the second example, the initial forests are as follows.
  
  <image>
  
  We can add an edge (2, 4).
  
  <image>
solution: import random as _random
  import sys as _sys
  
  
  def _main():
      [tests_n] = [1]
      for i_test in range(tests_n):
          [n, m_1, m_2] = _read_ints()
          edges_1 = tuple(_read_n_egdes(m_1))
          edges_2 = tuple(_read_n_egdes(m_2))
          random = _random.Random(_random.SystemRandom().getrandbits(256))
          new_edges = add_max_edges_n(n, edges_1, edges_2, random=random)
          print(len(new_edges))
          for u, v in new_edges:
              print(u+1, v+1)
  
  
  def add_max_edges_n(nodes_n, edges_1, edges_2, *, random):
      colors_1 = _build_dsu_by_edges(edges_1, nodes_n)
      colors_2 = _build_dsu_by_edges(edges_2, nodes_n)
      del edges_1, edges_2
      
      new_edges = _try_add_random_edges(nodes_n, colors_1, colors_2, random, max_failed_attempts_n=16)
      
      for u in range(nodes_n):
          for v in range(u+1, nodes_n):
              if not _same_owner(colors_1, u, v) and not _same_owner(colors_2, u, v):
                  new_edges.append((u, v))
                  _merge_owners(colors_1, u, v)
                  _merge_owners(colors_2, u, v)
      
      return new_edges
  
  
  def _try_add_random_edges(nodes_n, colors_1, colors_2, random, *, max_failed_attempts_n):
      new_edges = []
      
      if nodes_n < 2:
          return new_edges
      
      failed_attempts_n = 0
      while failed_attempts_n < max_failed_attempts_n:
          u = random.randrange(nodes_n-1)
          v = random.randrange(u+1, nodes_n)
          if not _same_owner(colors_1, u, v) and not _same_owner(colors_2, u, v):
              new_edges.append((u, v))
              _merge_owners(colors_1, u, v)
              _merge_owners(colors_2, u, v)
              failed_attempts_n = 0
          else:
              failed_attempts_n += 1
      
      return new_edges
  
  
  def _build_dsu_by_edges(edges, nodes_n):
      colors = list(range(nodes_n))
      for u, v in edges:
          _merge_owners(colors, u, v)
      for node in range(nodes_n):
          _get_owner(colors, node)
      return colors
  
  
  def _same_owner(colors, node_1, node_2):
      return _get_owner(colors, node_1) == _get_owner(colors, node_2)
  
  
  def _merge_owners(colors, node_1, node_2):
      node_1 = _get_owner(colors, node_1)
      node_2 = _get_owner(colors, node_2)
      colors[node_2] = node_1
  
  
  def _get_owner(colors, node):
      to_fix = []
      while node != colors[node]:
          to_fix.append(node)
          node = colors[node]
      for x in to_fix:
          colors[x] = node
      return node
  
  
  def _read_n_egdes(edges_n):
      edges = (_read_ints() for i_edge in range(edges_n))
      edges = ((u-1, v-1) for u, v in edges)
      return edges
  
  
  def _read_ints():
      return map(int, _read_string().split())
  
  
  def _read_string():
      result = _sys.stdin.readline()
      assert result and result[-1] == '\n'
      return result[:-1]
  
  
  if __name__ == '__main__':
      _main()
  