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

Ex Input:
Sentence: 'a table topped with a cupcake on a picture of a cupcake'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'a toilet sits in a cluttered bathroom next to a sink'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a couple of women standing next to a couple of soldiers'. Find frequency of the letter 'i'

Ex Output:

2