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

Ex Input:
Sentence: 'three woman are having a discussion in the kitchen'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'a girl laying on a bed posing for a picture'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'a person who is covering their face with their cell phone'. Find frequency of the letter 'i'

Ex Output:

5