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

Ex Input:
Sentence: 'two zebras standing around while a third zebra drinks from a pond'. Find frequency of the letter 's'

Ex Output:
3


Ex Input:
Sentence: 'two indian women in colorful garb standing barefoot with two indian men'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'the fire hydrant holds the pink teddy bear upright'. Find frequency of the letter 'i'

Ex Output:

3