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

Ex Input:
Sentence: 'slices of orange are arranged on a plate'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'two persons standing outside a moving sub train'. Find frequency of the letter 'a'

Ex Output:
3


Ex Input:
Sentence: 'an  image of a group of people playing soccer'. Find frequency of the letter 'e'

Ex Output:

4