Chapati Division

Siri prepares some chapatis for her family, which includes 3 sons. When the first son came home, he gives 1 chapati to the dog, and eats 1/3rd of the remaining chapatis .
When the second son came home, he gives 1 chapati to the dog, and eats 1/3rd of the remaining chapatis .
When the third son came home, he gives 1 chapati to the dog, and eats 1/3rd of the remaining chapatis .
Finally, in the evening, the three sons meet up, give 1 chapati to the dog and each eats 1/3rd of the remaining chapatis (hence there are none left).

In this entire process no single chapati is divided into fractions. What is the minimum number of chapatis that Siri made?