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

Ex Input:
Sentence: 'a crowd of people standing in front of a green train'. Find frequency of the letter 'g'

Ex Output:
2


Ex Input:
Sentence: 'the sun goes down over a bike tied to a bench at the beach'. Find frequency of the letter 't'

Ex Output:
5


Ex Input:
Sentence: 'a woman carrying a surfboard on top of a beach'. Find frequency of the letter 'c'

Ex Output:

2