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

Ex Input:
Sentence: 'a wedding cake with pink roses on a silver plate'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a lady mixes some things in a blender as people look on'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'a set of three vases filled with green plants'. Find frequency of the letter 'w'

Ex Output:

1