Dogs in the GoodDog Obedience School win a blue ribbon for learning how to sit, a green ribbon for learning how to roll over, and a white ribbon for learning how to stay. There are 100 dogs in the school. 62 have blue ribbons, 55 have green ribbons, and 63 have white ribbons. 32 have a blue ribbon and a green ribbon; 31 have a green ribbon and a white ribbon; 38 have a blue ribbon and a white ribbon. 16 have all three ribbons. How many dogs have not learned any tricks?