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

Ex Input:
Sentence: 'a small white dog looking out a car window'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'man is snow gear and skis skiing in the snow'. Find frequency of the letter 'i'

Ex Output:
5


Ex Input:
Sentence: 'black guy in a laker shirt and shorts'. Find frequency of the letter 'd'

Ex Output:

1