output_description: Print a positive integer not greater than 10^{18} that is a multiple of X but
  not a multiple of Y, or print -1 if it does not exist.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      X Y
attempt: import math
  
  input = str(input()).split(" ")
  for index in range(len(input)):
      input[index] = int(input[index])
  x = input[0]
  y = input[1]
  
  def ahaha(x, y):
      for index in range(1, min(abs(y), math.floor((10**(18))/x)):
          if (x * index % y != 0):
              return x * index
      return -1
  
  print(ahaha(x,y))
  
problem_description: Statement
  
  You are given positive integers X and Y. If there exists a positive integer
  not greater than 10^{18} that is a multiple of X but not a multiple of Y,
  choose one such integer and print it. If it does not exist, print -1.
samples: [{"input": "8 6", "output": "16\n    \n\nFor example, 16 is a multiple of 8 but not a multiple of 6.\n\n* * *"}, {"input": "3 3", "output": "-1\n    \n\nA multiple of 3 is a multiple of 3."}]