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

Ex Input:
Sentence: 'a black bear sitting in the grass taking a rest'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'a half eaten doughnut in a persons hand'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'a boat sitting on top of a beach next to water'. Find frequency of the letter 'g'

Ex Output:

1