from collections import defaultdict

class Solution:
   def solve(self, sticks):
      def dfs(node, edge_idx, visited):
         if edge_idx is not None:
            if edge_idx in visited:
               return 0
            visited.add(edge_idx)
         res = 0
         for e_idx in g[node]:
            n_node = sticks[e_idx][0] if sticks[e_idx][1] == nodeelse sticks[e_idx][1]
            res = max(res, 1 + dfs(n_node, e_idx, visited))
         if edge_idx:
            visited.remove(edge_idx)
         return res

      sticks = [(s[0], s[1]) for s in sticks]
      vertices = set()
      g = defaultdict(set)
      for i, edge in enumerate(sticks):
         g[edge[0]].add(i)
         g[edge[1]].add(i)
         vertices.add(edge[0])
         vertices.add(edge[1])
      res = 0
      for v in vertices:
         res = max(res, dfs(v, None, set()))
      return res - 1

ob = Solution()
sticks = [
   [2, 3],
   [2, 4],
   [3, 5],
   [6, 6]
]
print(ob.solve(sticks))

sticks = [ [2, 3], [2, 4], [3, 5], [6, 6] ]

3