input: def iscube(a):
      '''
      Write a Python function that accepts an integer a and determines 
      if it is a perfect cube of another integer, returning True if it is. 
      Note: you can assume the input is always valid.
      Examples:
      iscube(1) ==> True
      iscube(2) ==> False
      iscube(-1) ==> True
      iscube(64) ==> True
      iscube(0) ==> True
      iscube(180) ==> False
      '''
output:     cube_root = round(a ** (1/3))
      return cube_root ** 3 == a