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

Ex Input:
Sentence: 'a laptop computer with pictures of giraffes on the homescreen'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a construction sign is displayed on a street'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'a boat being rowed down the river between two buildings'. Find frequency of the letter 'l'

Ex Output:

1