In this task, you need to count the number of times the given letter appears in the given sentence.

Ex Input:
Sentence: 'a girl hitting a tennis ball on a court'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'a burning wood stove has a tea pot sitting on top of it and is full of wood'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'two hot dogs in foil loaded with toppings'. Find frequency of the letter 'p'

Ex Output:

2