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

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: 'a doll with huge eyes and black hair with blunt bangs holds a red umbrella'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a colorful passenger train pulled by a green engine'. Find frequency of the letter 'r'

Ex Output:

4