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

Ex Input:
Sentence: 'a doorway looking into a small bathroom with white toilet'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'three men are in a kitchen cooking and cutting through a dish'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'an old style bedroom with a bed, dresser and bed side table'. Find frequency of the letter 'm'

Ex Output:

1