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

Ex Input:
Sentence: 'a lady is standing near a luggage stand at the air port'. Find frequency of the letter 'a'

Ex Output:
9


Ex Input:
Sentence: 'a man in a black wet suit rides an orange surfboard on the water'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'a group of men sitting next to each other with baby girl and stuffed bear'. Find frequency of the letter 'e'

Ex Output:

6


