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: 'men are riding on motorcycles with a man riding in their carriers'. Find frequency of the letter 'r'

Ex Output:
8


Ex Input:
Sentence: 'a ball player holding his glove on the field'. Find frequency of the letter 'l'

Ex Output:

6