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

Ex Input:
Sentence: 'a man paddle boarding by a boat dock in a city'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'young boy flying kite in large field at outdoor event'. Find frequency of the letter 'y'

Ex Output:
3


Ex Input:
Sentence: 'the yellow and blue umbrella is open beside a stick'. Find frequency of the letter 'e'

Ex Output:

7