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

Ex Input:
Sentence: 'a group of workers washing and cleaning fruits and vegetables'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'a person with some scissors over a bowl'. Find frequency of the letter 's'

Ex Output:
6


Ex Input:
Sentence: 'an grey elephant roaming around the rocks outside'. Find frequency of the letter 'd'

Ex Output:

2