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

Ex Input:
Sentence: 'two young ladies that are dancing in the room together'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'an empty clean kitchen with island, marble countertops , stove and cabinetry'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'man riding on his personal motorcycle down the street'. Find frequency of the letter 'i'

Ex Output:

3