Не могу верно понять задачу из ЕГЭ по инфе. Почему ответ неверный?

with open('27-B.txt') as f:
    count_row = int(f.readline())
    count_even, count_odd, total_sum = 0, 0, 0
    diff_array = []
    for row in range(count_row):
        a, b = map(int, f.readline().split())
        max_number = max(a, b)
        if max_number % 2 == 0:
            count_even += 1
        else:
            count_odd += 1
        total_sum += max_number
        diff_array.append(abs(a - b))
 
diff_array = sorted(diff_array)
i = 0
while True:
    if count_even > count_odd and total_sum % 2 != 0:
        count_even -= 1
        count_odd += 1
        total_sum -= diff_array[i]
    elif count_odd > count_even and total_sum % 2 == 0:
        count_even += 1
        count_odd -= 1
        total_sum -= diff_array[i]
    else:
        print(total_sum)
        break
    i += 1

with open('27-B.txt') as f:
    count_row = int(f.readline())
    count_even, count_odd, total_sum = 0, 0, 0
    diff_parity_more_less_array = []  # [разница; 10 – разной чётности при большем чётном, 01 – разной чётности при большем нечётном, 00 – одинаковой чётности]
    for row in range(count_row):
        numbers_array = sorted(list(map(int, f.readline().split())))
        max_number = numbers_array[1]
        if max_number % 2 == 0:
            count_even += 1
        else:
            count_odd += 1
        total_sum += max_number
        a, b = numbers_array
        if a % 2 == b % 2:
            diff_parity_more_less_array.append([abs(a - b), '00'])
        else:
            if a % 2 == 0:
                diff_parity_more_less_array.append([abs(a - b), '01'])
            else:
                diff_parity_more_less_array.append([abs(a - b), '01'])
 
diff_parity_more_less_array = sorted(diff_parity_more_less_array)
i = 0
while True:
    if count_even > count_odd and total_sum % 2 != 0 or count_odd > count_even and total_sum % 2 == 0:
        total_sum -= diff_parity_more_less_array[i][0]
        if diff_parity_more_less_array[i][1] == '01':
            count_even += 1
            count_odd -= 1
        elif diff_parity_more_less_array[i][1] == '10':
            count_even -= 1
            count_odd += 1
    else:
        print(total_sum)
        break
    i += 1

with open('27-B.txt') as f:
    count_row = int(f.readline())
    count_even, count_odd, total_sum = 0, 0, 0
    diff_parity_more_less_array = []  # [разница; 10 – разной чётности при большем чётном, 01 – разной чётности при большем нечётном, 00 – одинаковой чётности]
    for row in range(count_row):
        numbers_array = sorted(list(map(int, f.readline().split())))
        max_number = numbers_array[1]
        if max_number % 2 == 0:
            count_even += 1
        else:
            count_odd += 1
        total_sum += max_number
        if (numbers_array[0] + numbers_array[1]) % 2 == 0:
            diff_parity_more_less_array.append([abs(numbers_array[0] - numbers_array[1]), '00'])
        else:
            if numbers_array[1] % 2 == 0:
                diff_parity_more_less_array.append([abs(numbers_array[0] - numbers_array[1]), '10'])
            else:
                diff_parity_more_less_array.append([abs(numbers_array[0] - numbers_array[1]), '01'])
 
diff_parity_more_less_array = sorted(diff_parity_more_less_array)
i = 0
while True:
    if count_even > count_odd and total_sum % 2 != 0 or count_odd > count_even and total_sum % 2 == 0:
        total_sum -= diff_parity_more_less_array[i][0]
        if diff_parity_more_less_array[i][1] == '01':
            count_even += 1
            count_odd -= 1
        elif diff_parity_more_less_array[i][1] == '10':
            count_even -= 1
            count_odd += 1
    else:
        print(total_sum)
        break
    i += 1

with open('27-B.txt') as f:
    count_row = int(f.readline())
    count_eo = total_sum = 0
    diff_01, diff_10 = [], []
 
    for row in range(count_row):
        a, b = map(int, f.readline().split())
        if a > b:
            a, b = b, a
        total_sum += b
        count_eo += 1 - 2 * (b%2)
        if (a+b)%2:
            if b%2:
                diff_01.append(b-a)
            else:
                diff_10.append(b-a)
 
if total_sum%2 == 0 and count_eo<0:
    total_sum -= min(min(diff_10),
     sum(sorted(diff_01)[:1-count_eo]))
     
elif total_sum%2 and count_eo>0:
    total_sum -= min(min(diff_01),
     sum(sorted(diff_10)[:count_eo+1]))
     
elif count_eo == 0:
    
    if total_sum%2:
        total_sum -= min(min(diff_01),
         sum(sorted(diff_10)[:2]))
         
    else:
        if diff_11:
            total_sum -= min(min(diff_10),
                 sum(sorted(diff_01)[:2]))
        
print(total_sum)