3.py

#!/usr/bin/env python3

def is_n_digit(number: int, digits: int) -> bool:
    return len(str(abs(number))) == digits

file = open("17.txt", "r")
numbers = list(map(int, file.readlines()))
max_strange_num = 0
for element in numbers:
    if not str(element).endswith("15"):
        continue
    max_strange_num = max(max_strange_num, element)
valid_triples_num = 0
minimal_sum_num = 0
for i in range(len(numbers) - 2):
    distance = numbers[i:i + 3]
    a, b, c = distance
    total = sum(distance)
    if list(map(is_n_digit, distance, [4] * 3)).count(True) == 1 and \
            total < max_strange_num:
        valid_triples_num += 1
        minimal_sum_num = min(minimal_sum_num, total)

print(valid_triples_num, minimal_sum_num)
file.close()