There are two things I want to ask you about this time.
First of all, I don't know why the error occurred.
Next, I am wondering if an unnatural indentation will occur when trying to break a line.

Error message
SyntaxError: invalid syntax
Applicable source code
nums = [int (e) for e in input (). split ()] #A, B, X
A, B, X = nums [0], nums [1], nums [2]
N_prices (n) = A * n + B * (len (str (n))

if X<= N_prices (0):
    print ('0')
if N_prices (10 ** 9)<= X:
    print ('109')
for i in range (1, 10 ** 9):
    if X<= N_prices (i) and X<= N_prices (i + 1):
        print (str (i))

Checked for unnecessary whitespace at the end, but it didn't seem

Supplemental information (FW/tool version etc.)

jupyter notebook, python 3.7.3