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

Ex Input:
Sentence: 'small airplane in the process of taking off'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a woman and a child walking down a street with a kite'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'two giraffes trying to reach grass in a basket over their head'. Find frequency of the letter 't'

Ex Output:

5