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

Ex Input:
Sentence: 'a girl laying on a bed posing for a picture'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'a room with a big screen television and a couch'. Find frequency of the letter 'h'

Ex Output:
2


Ex Input:
Sentence: 'a man standing next to a small airplane'. Find frequency of the letter 'l'

Ex Output:

3