from typing import Tuple
import itertools


def part1(values: Tuple[int, ...]) -> int:
    """ Identify a value which is not the sum of the 25 preceding values, and return it """
    for i in range(len(values) - 25):
        target = values[i + 25]
        for j, k in itertools.product(range(i, i + 25), range(i, i + 25)):
            if j != k and values[j] + values[k] == target:
                break
        else:
            return target
    raise RuntimeError('Failed to find a value!')