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

Ex Input:
Sentence: 'a group of men standing on the side of a boat'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a couple is cutting in to a cake at a wedding'. Find frequency of the letter 'd'

Ex Output:
2


Ex Input:
Sentence: 'a small boy sitting on a homemade skateboard'. Find frequency of the letter 'l'

Ex Output:

2