checksum_part1

Given the first 11 digits of a GTIN-12 barcode as an integer (i.e. without leading zeros), determine the last number by calculating the value of the check digit.

Example:

• For a = 29104150021, the output should be checksum_part1(a) = 9.

The digit sum can be calculated as follows, using the information in the link above:

You know that you need to multiply the digit at N1 by 3, the digit at N2 by 1, and so on, then add these numbers together: 2 * 3 + 9 * 1 + 1 * 3 + 0 * 1 + 4 * 3 + 1 * 1 + 5 * 3 + 0 * 1 + 0 * 3 + 2 * 1 + 1 * 3 = 51

Then, you need to subtract that sum from the nearest equal or higher multiple of ten: 60 - 51 = 9.

Input/Output:

• [execution time limit] 0.5 seconds 

• [input] integer64 barcode

1 ≤ barcode < 1011.

• [output] integer

  The last digit of the barcode.