output_description: If there is a price that satisfies the condition, print an integer
  representing the lowest such price; otherwise, print `-1`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      A B
attempt: A, B = [int(n) for n in input().split()]
  XA = 100 * A // 8
  XB = 10 * B
  r = abs(XA - XB) * 0.1
  print(-1 if r > 0.9 else max(XA, XB))
  
problem_description: Statement
  
  Find the price of a product before tax such that, when the consumption tax
  rate is 8 percent and 10 percent, the amount of consumption tax levied on it
  is A yen and B yen, respectively. (Yen is the currency of Japan.)
  
  Here, the price before tax must be a positive integer, and the amount of
  consumption tax is rounded down to the nearest integer.
  
  If multiple prices satisfy the condition, print the lowest such price; if no
  price satisfies the condition, print `-1`.
samples: [{"input": "2 2", "output": "25\n    \n\nIf the price of a product before tax is 25 yen, the amount of consumption tax\nlevied on it is:\n\n  * When the consumption tax rate is 8 percent: \\lfloor 25 \\times 0.08 \\rfloor = \\lfloor 2 \\rfloor = 2 yen.\n  * When the consumption tax rate is 10 percent: \\lfloor 25 \\times 0.1 \\rfloor = \\lfloor 2.5 \\rfloor = 2 yen.\n\nThus, the price of 25 yen satisfies the condition. There are other possible\nprices, such as 26 yen, but print the minimum such price, 25.\n\n* * *"}, {"input": "8 10", "output": "100\n    \n\nIf the price of a product before tax is 100 yen, the amount of consumption tax\nlevied on it is:\n\n  * When the consumption tax rate is 8 percent: \\lfloor 100 \\times 0.08 \\rfloor = 8 yen.\n  * When the consumption tax rate is 10 percent: \\lfloor 100 \\times 0.1 \\rfloor = 10 yen.\n\n* * *"}, {"input": "19 99", "output": "-1\n    \n\nThere is no price before tax satisfying this condition, so print `-1`."}]