output_description: Print his Inner Rating.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N R
attempt: n, a, b = map(int, input().split())
  mod = pow(10, 9) + 7
  
  
  def comb(N, x):
      numerator = 1
      for i in range(N - x + 1, N + 1):
          numerator = numerator * i % mod
      denominator = 1
      for j in range(1, x + 1):
          denominator = denominator * j % mod
      d = pow(denominator, mod - 2, mod)
      return numerator * d
  
  
  a = comb(n, a)
  b = comb(n, b)
  
  print((pow(2, n, mod) - 1 - a - b) % mod)
  
problem_description: Statement
  
  Takahashi is a member of a programming competition site, _ButCoder_.
  
  Each member of ButCoder is assigned two values: **Inner Rating** and
  **Displayed Rating**.
  
  The Displayed Rating of a member is equal to their Inner Rating if the member
  has participated in 10 or more contests. Otherwise, the Displayed Rating will
  be their Inner Rating minus 100 \times (10 - K) when the member has
  participated in K contests.
  
  Takahashi has participated in N contests, and his Displayed Rating is R. Find
  his Inner Rating.
samples: [{"input": "2 2919", "output": "3719\n    \n\nTakahashi has participated in 2 contests, which is less than 10, so his\nDisplayed Rating is his Inner Rating minus 100 \\times (10 - 2) = 800.\n\nThus, Takahashi's Inner Rating is 2919 + 800 = 3719.\n\n* * *"}, {"input": "22 3051", "output": "3051"}]