How to fix TypeError: unsupported operand type(s) for +: 'int' and 'str'?

Question

Python

s = input("введи штрих код")
pudge = 0
a =''
b =''
for i in range(0,len(s),2):
    a += s[i]
for i in range(1, len(s), 2):
    b += s[i]
gg = list(a)
gg1 = list(b)
print(sum(gg))
print(gg1)

Answer 1

Obviously don't add numbers to strings.

Answer 2

int(value) + int(value) or str(value) + str(value)