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

Ex Input:
Sentence: 'a man riding a skateboard up the side of a ramp'. Find frequency of the letter 'u'

Ex Output:
1


Ex Input:
Sentence: 'a half eaten doughnut in a persons hand'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'a holstein cow lets birds rest on him in the pasture'. Find frequency of the letter 't'

Ex Output:

5