l Problem
A 13digit string will be presented after the barcode is scanned. In order to deal with the scanning mistake , the method of calculateing checksum is used to inspect whether the barcode is errorfree or not. Detailed calculation process is as follows:
Extract the first 12 digits from the 13digit string, add the numbers at odd positions to obtain a sum S1, and add the numbers at even positions to obtain a sum S2. Subtract S2 from S1, perform a mod with the result and 10 to obtain the remainder, and compute the absolute value. The result should be the 13^{th} digit of the barcode. Otherwise, this barcode is not correct.
Evaluate the correctness of a given barcode.
l Tip
General steps: Convert the 13 digits of the given barcode into a sequence, find out the sum of numbers at odd positions and that at even positions among the first 12 digits in the sequence, implement subtraction for the two sums, then perform a mod with the difference and 10 to obtain a remainder, whose absolute value will then be found, finally evaluate whether the result is equal to the last digit of the barcode.
l Code

A 

1 
="1234567890123" 
The given barcode 
2 
=A1.split@p() 
Convert the barcode into a sequence 
3 
=A2(to(12)).step(2,1).sum() 
The sum of numbers on odd digits for the first 12 digits 
4 
=A2(to(12)).step(2,2).sum() 
The sum of numbers on even digits for the first 12 digits 
5 
=abs((A3A4)%10) 
The difference between the two sums, mod 10, take the remainder's absolute value 
6 
=A5==A2.m(1) 
Evaluate whether the result of A5 is the same as the number on the last digit of the barcode 
l Result