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

Ex Input:
Sentence: 'a teddy bear is sitting on a heart shaped patio chair outside'. Find frequency of the letter 'i'

Ex Output:
6


Ex Input:
Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'

Ex Output:
7


Ex Input:
Sentence: 'a skier skiing with her poles tucked under her arms'. Find frequency of the letter 'c'

Ex Output:

1