output_description: Print the number of bouquets that Akari can make, modulo (10^9 + 7). (If there
  are no such bouquets, print `0`.)
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      n a b
attempt: n, a, b = list(map(int, input().split(" ")))
  
  # 二項係数 mod [検索]
  mmm = 1000000000 + 7
  fac = []
  inv = []
  inv_fac = []
  
  
  def init(n):
      fac.append(1)
      fac.append(1)
      inv.append(0)
      inv.append(1)
      inv_fac.append(1)
      inv_fac.append(1)
      for i in range(2, n):
          fac.append(fac[-1] * i % mmm)
          inv.append(mmm - inv[mmm % i] * (mmm // i) % mmm)
          inv_fac.append(inv_fac[-1] * inv[-1] % mmm)
  
  
  def choice(a, b):
      if a < b:
          return 0
      v = 1
      for i in range(b):
          v = (
              v * (a - i)
          ) % mmm  # 偶然通っていたけどここはnではなくa (eの途中で気づいた)
      return v * inv_fac[b]
  
  
  init(int(2e5) + 1)
  
  
  ans = pow(2, n, mmm) - 1  # v, e, mod
  bunshi = 1
  for i in range(a):
      bunshi = (bunshi * (n - i)) % mmm
  ans -= choice(n, a)
  ans -= choice(n, b)
  print(ans % mmm)
  
  """
  4, 1, 3 => 4c2 + 4c4 -> 6+1 = 7
  4 + 6 + 4 + 1 - 4c1 - 4c2 
  1        1
  11       2
  121      4
  1331     8
  14641   16, 0が無いので-1, 大きい combination -> 二項係数 mod [検索]
  """
  
problem_description: Statement
  
  Akari has n kinds of flowers, one of each kind.
  
  She is going to choose one or more of these flowers to make a bouquet.
  
  However, she hates two numbers a and b, so the number of flowers in the
  bouquet cannot be a or b.
  
  How many different bouquets are there that Akari can make?
  
  Find the count modulo (10^9 + 7).
  
  Here, two bouquets are considered different when there is a flower that is
  used in one of the bouquets but not in the other bouquet.
samples: [{"input": "4 1 3", "output": "7\n    \n\nIn this case, Akari can choose 2 or 4 flowers to make the bouquet.\n\nThere are 6 ways to choose 2 out of the 4 flowers, and 1 way to choose 4, so\nthere are a total of 7 different bouquets that Akari can make.\n\n* * *"}, {"input": "1000000000 141421 173205", "output": "34076506\n    \n\nPrint the count modulo (10^9 + 7)."}]