output_description: Print the maximum number of times we can do the operation.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      x_1 y_1
      :
      x_N y_N
attempt: import sys
  from bisect import bisect_left
  
  sr = lambda: sys.stdin.readline().rstrip()
  ir = lambda: int(sr())
  lr = lambda: list(map(int, sr().split()))
  
  N = ir()
  XY = [lr() for _ in range(N)]
  V = list(range(2 * 10**5 + 1))  # 1-indexed X coordinate、Y coordinateの順番
  
  
  # Aでxの根を求める
  def find(A, x):
      p = A[x]
      if p == x:
          return x
      a = find(A, p)
      A[x] = a
      return a
  
  
  # Aでxとyの属する集合の併合
  def union(A, x, y):
      if find(A, x) > find(A, y):
          bx, by = find(A, y), find(A, x)
      else:
          bx, by = find(A, x), find(A, y)
      A[by] = bx  # 根をbxに統一
  
  
  for x, y in XY:
      y += 10**5
      if find(V, x) != find(V, y):
          union(V, x, y)
  
  set_V = [set() for _ in range(2 * 10**5 + 1)]  # 1-indexed
  for x, y in XY:
      root = find(V, x)
      set_V[root] |= set([x, y + 10**5])
  
  set_V = [x for x in set_V if x]
  answer = 0
  for z in set_V:
      z = sorted(list(z))
      cnt_x = bisect_left(z, 10**5 + 1)
      cnt_y = len(z) - cnt_x
      answer += cnt_x * cnt_y
  
  answer -= N
  print(answer)
  # 48
  
problem_description: Statement
  
  There are N dots in a two-dimensional plane. The coordinates of the i-th dot
  are (x_i, y_i).
  
  We will repeat the following operation as long as possible:
  
    * Choose four integers a, b, c, d (a \neq c, b \neq d) such that there are dots at exactly three of the positions (a, b), (a, d), (c, b) and (c, d), and add a dot at the remaining position.
  
  We can prove that we can only do this operation a finite number of times. Find
  the maximum number of times we can do the operation.
samples: [{"input": "3\n    1 1\n    5 1\n    5 5", "output": "1\n    \n\nBy choosing a = 1, b = 1, c = 5, d = 5, we can add a dot at (1, 5). We cannot\ndo the operation any more, so the maximum number of operations is 1.\n\n* * *"}, {"input": "2\n    10 10\n    20 20", "output": "0\n    \n\nThere are only two dots, so we cannot do the operation at all.\n\n* * *"}, {"input": "9\n    1 1\n    2 1\n    3 1\n    4 1\n    5 1\n    1 2\n    1 3\n    1 4\n    1 5", "output": "16\n    \n\nWe can do the operation for all choices of the form a = 1, b = 1, c = i, d = j\n(2 \\leq i,j \\leq 5), and no more. Thus, the maximum number of operations is\n16."}]