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

Ex Input:
Sentence: 'a number of small boats on a beach near an umbrella'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'a wedding cake with pink roses on a silver plate'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a dog a cat and a teddy bear all on a bed together'. Find frequency of the letter 't'

Ex Output:

4