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

Ex Input:
Sentence: 'young girl playing with refrigerator magnet while kneeling on floor'. Find frequency of the letter 'n'

Ex Output:
6


Ex Input:
Sentence: 'a man playing baseball on a television set'. Find frequency of the letter 'l'

Ex Output:
4


Ex Input:
Sentence: 'people with masks are making food on a table'. Find frequency of the letter 'e'

Ex Output:

4