input: def iscube(a):
      '''
      Write a Python function that accepts an integer a and returns True 
      if the integer is a perfect cube.
      Note: 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:     cuberoot = round(a ** (1/3))
      return cuberoot**3 == a