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 = (int(x) for x in input().split())
  mod = 1000000007
  n1 = int(n / 2)
  list = [1]
  for i in range(n1):
      k = list[i] * (n - i) / (i + 1)
      k %= mod
      list.append(k)
  su = sum(list) % mod
  su *= 2
  if n % 2 == 0:
      su -= list[n1]
  if 2 * a >= n:
      a = n1 - (a / 2)
  if 2 * b >= n:
      b = n1 - int(b / 2)
  su -= list[a]
  su -= list[b]
  su -= 1
  print(int(su % mod))
  
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)."}]