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

Ex Input:
Sentence: 'a couple of girls are hanging out at a restaurant'. Find frequency of the letter 'l'

Ex Output:
2


Ex Input:
Sentence: 'vanity sitting atop a base with two doors and a mirror overhead'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'a glass case containing a uniform and baseball stuff'. Find frequency of the letter 'n'

Ex Output:

5