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

Ex Input:
Sentence: 'a train going over a bridge with some buildings in the background'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'supplies and tools are arranged on the floor with a hard hat and bag'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a young child takes a ride on a skate ramp'. Find frequency of the letter 'a'

Ex Output:

6