input: Write a python function to calculate the difference between the sum of digits at even positions and the sum of digits at odd positions.
  assert check_diff(12345) == False
  assert check_diff(1212112) == True
  assert check_diff(1212) == False
output: def check_diff(num):
      num_str = str(num)
      even_sum = 0
      odd_sum = 0
      for i, digit in enumerate(num_str):
          if i % 2 == 0:
              even_sum += int(digit)
          else:
              odd_sum += int(digit)
      return even_sum == odd_sum