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

Ex Input:
Sentence: 'a scene at night; a plane alone on a runway with lit-up city buildings on the horizon'. Find frequency of the letter 'w'

Ex Output:
2


Ex Input:
Sentence: 'pizza with different vegetables sitting on top of a wooden slab'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'

Ex Output:

3