A survey was conducted among 50 people on the "Dish for the Day" they wanted. It was found out that 28 wanted Adobo, 15 wanted Munggo and 20 wanted Kare-Kare. Furthermore, 8 wanted Adobo and Kare-Kare, 7 wanted Adobo and Munggo, 10 wanted Munggo and Kare-Kare and 4 wanted all the dishes. How many people wanted Adobo only?