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

Ex Input:
Sentence: 'some people sitting on surfboards in the water'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'a couple of items that are on the wall'. Find frequency of the letter 'm'

Ex Output:
1


Ex Input:
Sentence: 'the pizza is cut into 5 triangle pieces'. Find frequency of the letter 'l'

Ex Output:

1