Finds most popular product in all websites.
Finds the biggest bargain data for each product and website.
Finds products that are not listed in any of the websites.
./homework2 add product 1,phone1,desc1,brand1
./homework2 add products < input1.txt
./homework2 add website URL1,country1,City1,ZipCode1,Street1,E-mail1
./homework2 add sell 1,URL1,2020-05-18,100,70
./homework2 delete product 1
./homework2 delete sell 1,URL1
./homework2 query 1
./homework2 query 2
./homework2 query 3