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

Ex Input:
Sentence: 'a river with a long dragon boat in it and rowers on the boat in sets of two, along with two other people'. Find frequency of the letter 'h'

Ex Output:
4


Ex Input:
Sentence: 'the large modern train is on the train track'. Find frequency of the letter 'm'

Ex Output:
1


Ex Input:
Sentence: 'a close up of a giraffe standing inside a fenced enclosure'. Find frequency of the letter 'e'

Ex Output:

7