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

Ex Input:
Sentence: 'an commercial airline airplane flies above the clouds'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'two women standing next to each other holding tennis rackets'. Find frequency of the letter 't'

Ex Output:
7


Ex Input:
Sentence: 'a kitchen with an odd shaped counter top with a metallic stove oven'. Find frequency of the letter 'n'

Ex Output:

4