Buggy python submission (verdict: Runtime Error):
def to_bin(number):
    return bin(number)[2:].zfill(45)


def xor(num1, num2):

    num1_str = to_bin(num1)
    num2_str = to_bin(num2)

    result = [0] * 45

    for digit in range(0, 45):
        result[digit] += int(num1_str[digit])
        result[digit] += int(num2_str[digit])

    result_str = ''

    for digit in result:

        if digit % 2 == 0:
            result_str += '0'
        else:
            result_str += '1'
    return int(result_str,2)


def f(a, b):
    return xor(g(a - 1), g(b))


def g(num):

    others = 0

    if num % 2 == 0:
        if (num // 2) % 2 != 0:
            others = 1

        return xor(num, others)
    else:
        if ((num - 1) // 2) % 2 != 0:
            others = 1

        return xor(xor(num, others), num - 1)


A, B = map(int, input().split())

result = f(A, B)

print(result)


Fixed submission:
def to_bin(number):

    return bin(number)[2:].zfill(45)


def xor(num1, num2):

    num1_str = to_bin(num1)
    num2_str = to_bin(num2)

    result_list = [0] * 45

    for digit in range(0, 45):
        result_list[digit] += int(num1_str[digit])
        result_list[digit] += int(num2_str[digit])

    result_str = ''

    for digit in result_list:

        if digit % 2 == 0:
            result_str += '0'
        else:
            result_str += '1'
    return int(result_str, 2)


def f(a, b):
    if a > 0:
        a -= 1

    return xor(g(a), g(b))


def g(num):

    others = 0

    if num % 2 == 0:
        if (num // 2) % 2 != 0:
            others = 1

        return xor(num, others)
    else:
        if ((num - 1) // 2) % 2 != 0:
            others = 1

        return xor(xor(num, others), num - 1)


A, B = map(int, input().split())

result = f(A, B)

print(result)

Buggy python submission (verdict: Time Limit Exceeded):
def to_bin(number):
    return bin(number)[2:].zfill(45)


A, B = map(int, input().split())

a_bin = bin(A)[2:].zfill(45)
b_bin = bin(B)[2:].zfill(45)

result = [0] * 45

for digit in range(0, 45):
    for num in range(A, B + 1):

        num_bin = to_bin(num)

        if result[digit] + int(num_bin[digit]) == 1:
            result[digit] = 1
        else:
            result[digit] = 0

result_str = ''

for digit in result:
    result_str += str(digit)


print(int(result_str, 2))


Fixed submission:
def to_bin(number):

    return bin(number)[2:].zfill(45)


def xor(num1, num2):

    num1_str = to_bin(num1)
    num2_str = to_bin(num2)

    result_list = [0] * 45

    for digit in range(0, 45):
        result_list[digit] += int(num1_str[digit])
        result_list[digit] += int(num2_str[digit])

    result_str = ''

    for digit in result_list:

        if digit % 2 == 0:
            result_str += '0'
        else:
            result_str += '1'
    return int(result_str, 2)


def f(a, b):
    if a > 0:
        a -= 1

    return xor(g(a), g(b))


def g(num):

    others = 0

    if num % 2 == 0:
        if (num // 2) % 2 != 0:
            others = 1

        return xor(num, others)
    else:
        if ((num - 1) // 2) % 2 != 0:
            others = 1

        return xor(xor(num, others), num - 1)


A, B = map(int, input().split())

result = f(A, B)

print(result)