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

Ex Input:
Sentence: 'a street scene looking at the back of the stop sign'. Find frequency of the letter 't'

Ex Output:
6


Ex Input:
Sentence: 'a plastic plastic plate topped with three different type of food'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'a table and white stove in a room'. Find frequency of the letter 'd'

Ex Output:

1