https://inf-ege.sdamgia.ru/test?theme=416

import numpy as np

# file_in = '27-demo.txt'  # 32
file_in = '27-B_demo.txt'  # 399762080
# file_in = '27-A_demo.txt'  # 127127

x = np.fromfile(file_in, sep=' ', dtype=np.int16)
count = x[0]
array = x[1:].reshape(count, 2)
array = np.sort(array)
sum_ = array[:, 1].sum()

array = np.array(sorted(array.tolist(), key=lambda x: x[1] - x[0])).reshape(count, 2)

for elem in array:
    if (sum_ - elem[1] + elem[0]) % 3 != 0:
        break
print(sum_ - elem[1] + elem[0])