input: 
  import numpy as np
  
  def runningTotal(arr):
      """ Return an array with the running total of numbers in the given list.
      >>> runningTotal([1, 2, 3, 4, 5])
      array([ 1,  3,  6, 10, 15])
      >>> runningTotal([10, -10, 10, -10, 10])
      array([10,  0, 10,  0, 10])
      """
      return np.cumsum(arr)
  
output:     return np.cumsum(arr)