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

Ex Input:
Sentence: 'there is an old stove with old pots on the burners'. Find frequency of the letter 't'

Ex Output:
5


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: 'a man riding a motorcycle through the center of a tree'. Find frequency of the letter 'f'

Ex Output:

1