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

Ex Input:
Sentence: 'a man with a large grey and black beard and glasses and a tie'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a woman in a messy kitchen with a child'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a man who is skiing down a snowy hill'. Find frequency of the letter 'o'

Ex Output:

3