Create a Python function that takes in an array-like data structure and returns the difference of its maximum and minimum values.
[100, 45, 56, 30, 90, 100]
def get_difference(arr):
    return max(arr) - min(arr)

input_arr = [100, 45, 56, 30, 90, 100]
difference = get_difference(input_arr)
print(difference)  # Output: 70