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

Ex Input:
Sentence: 'man in a sleeping bag on the floor using a laptop computer'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'cars parked outside if a retail store'. Find frequency of the letter 'd'

Ex Output:
2


Ex Input:
Sentence: 'a painting of a skateboarder going down the railing'. Find frequency of the letter 't'

Ex Output:

3