output_description: Among A, B and C, print the integer that is different from the rest.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      A B C
attempt: import copy
  
  
  def set(adjacent, edge):
      for x in edge:
          adjacent[x[0]].append(x[1])
          adjacent[x[1]].append(x[0])
  
  
  def search(goal, path):
      n = path[len(path) - 1]
      if n == goal:
          print(path)
      else:
          for x in adjacent[n]:
              if x not in path:
                  path.append(x)
                  search(goal, path)
                  path.pop()
  
  
  def search_loop_node(adjacent, start, path, node_loops):
      n = path[len(path) - 1]
      for x in adjacent[n]:
          if x == start and len(path) >= 2 and path[-2] != start:
              path.append(x)
              node_loops.append(copy.deepcopy(path))
              path.pop()
          elif x not in path:
              path.append(x)
              search_loop_node(adjacent, start, path, node_loops)
              path.pop()
  
  
  def main():
      # 入力
      N, M = [int(i) for i in input().split()]
      edge = []
      for i in range(M):
          a, b = [int(i) for i in input().split()]
          edge.append([a, b])
  
      # 辺の生成
      adjacent = [[] for i in range(N + 1)]
      loops = []
      set(adjacent, edge)
      # ループの検索
      for i in range(N):
          search_loop_node(adjacent, i, [i], loops)
      # ループに属する辺(橋でない辺)の検索
      not_bridge = []
      for loop in loops:
          pre_node = loop[0]
          for node in loop:
              if pre_node < node and [pre_node, node] not in not_bridge:
                  not_bridge.append([pre_node, node])
              pre_node = node
      # 答えは全体の辺の数からループでないものを引いた数
      print(M - len(not_bridge))
  
  
  if __name__ == "__main__":
      main()
  
problem_description: Statement
  
  You are given three integers, A, B and C.  
  Among them, two are the same, but the remaining one is different from the
  rest.  
  For example, when A=5,B=7,C=5, A and C are the same, but B is different.  
  Find the one that is different from the rest among the given three integers.
samples: [{"input": "5 7 5", "output": "7\n    \n\nThis is the same case as the one in the statement.\n\n* * *"}, {"input": "1 1 7", "output": "7\n    \n\nIn this case, C is the one we seek.\n\n* * *"}, {"input": "-100 100 100", "output": "-100"}]