ModAdd

import fileinput

with fileinput.input(['z']) as input:
    a = list(input.readline().rstrip())[::-1]
    b = list(input.readline().rstrip())[::-1]
    res = []
    z = min(len(a), len(b))
    for i in range(z):
        res.append(str((int(a[i]) + int(b[i])) % 10))
    if len(a) > len(b):
        res.extend(a[z:])
    elif len(a) < len(b):
        res.extend(b[z:])
    print(int(''.join(res[::-1])))

Test 1

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 2

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 3

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 4

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 5

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 6

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 4, in <module>
    a = lis...