output_description: Print the number of ways she can travel to the bottom-right cell, modulo
  10^9+7.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      H W A B
attempt: H, W, A, B = map(int, input().split())
  
  MOD = 10**9 + 7
  
  
  def count_dr(d, r):
      # H+WCW
      cnt = 1
      multiple_nums = list(range(d + r, d, -1))
      divide_nums = list(range(1, r + 1))
      for num in multiple_nums:
          cnt *= num % MOD
  
      for num in divide_nums:
          cnt = cnt // num
  
      return cnt
  
  
  def zouka_combination(zouka, kotei, how_many):
      tmp = count_dr(zouka, kotei)
      #     print(tmp)
      #     tmp_last = count_dr(a,w-b-1)
      result = []
      for i in range(1, how_many + 1):
          numer = zouka + kotei + i
          denom = zouka + i
          tmp *= numer
          tmp //= denom
          result.append(tmp)
      return result
  
  
  exit = zouka_combination(H - A - 1, B - 1, A)
  last = ([1] + zouka_combination(0, W - B - 1, A - 1))[::-1]
  
  cnt = 0
  for e, l in zip(exit, last):
      cnt += e * l
      cnt %= MOD
  print(count_dr(H - 1, W - 1) - cnt)
  
problem_description: Statement
  
  We have a large square grid with H rows and W columns. Iroha is now standing
  in the top-left cell. She will repeat going right or down to the adjacent
  cell, until she reaches the bottom-right cell.
  
  However, she cannot enter the cells in the intersection of the bottom A rows
  and the leftmost B columns. (That is, there are A×B forbidden cells.) There is
  no restriction on entering the other cells.
  
  Find the number of ways she can travel to the bottom-right cell.
  
  Since this number can be extremely large, print the number modulo 10^9+7.
samples: [{"input": "2 3 1 1", "output": "2\n    \n\nWe have a 2\u00d73 grid, but entering the bottom-left cell is forbidden. The number\nof ways to travel is two: \"Right, Right, Down\" and \"Right, Down, Right\".\n\n* * *"}, {"input": "10 7 3 4", "output": "3570\n    \n\nThere are 12 forbidden cells.\n\n* * *"}, {"input": "100000 100000 99999 99999", "output": "1\n    \n\n* * *"}, {"input": "100000 100000 44444 55555", "output": "738162020"}]