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

Ex Input:
Sentence: 'four men standing around two pizzas in a conference room'. Find frequency of the letter 't'

Ex Output:
2


Ex Input:
Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'

Ex Output:
10


Ex Input:
Sentence: 'the two images are of a young child in a baseball hat and jacket'. Find frequency of the letter 'd'

Ex Output:

2