Prince or Impostor

In ancient Persia, during prosperous times, there was a great king named Darius. One day, Darius's son was born, and no one was happier than the king. To celebrate, he organized a grand festival. However, during the celebrations, assassins hired by Darius's enemies infiltrated the palace and kidnapped the newborn prince. Enraged, Darius ordered the execution of the guards and announced a search, promising a substantial reward to anyone who could bring his son back to the palace.

Days turned into weeks, months, and years, but there was no sign of the prince. As the eighteenth year of searching began, a tall, slender young man with a spark in his eyes arrived at the palace, claiming to be the lost prince. He told incredible stories of being left with a humble fisherman's family who, under the threat of death, were ordered not to speak of the prince to anyone. On his deathbed, the old fisherman revealed the young man's true origins.

Darius was ready to accept the young man, but his vizier advised caution and suggested verifying his identity first. Every human cell contains DNA, a chain of nucleotides encoded by the symbols A, G, T, C. These chains should be similar among close relatives. The vizier proposed to take a fragment of the young man's DNA and compare it with the king's DNA, starting from a specific position. Ideally, the fragment would match exactly from the chosen position, but generally, the degree of similarity is determined by the number of matching symbols. The vizier and the king ask you to determine the starting position for the comparison that gives the highest similarity.