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

Ex Input:
Sentence: 'people waiting on a train platform in a wooded area'. Find frequency of the letter 'p'

Ex Output:
3


Ex Input:
Sentence: 'a plane with stairs next to it sitting in a large lot'. Find frequency of the letter 'i'

Ex Output:
6


Ex Input:
Sentence: 'a white toilet sitting in side of a bathroom stall'. Find frequency of the letter 'i'

Ex Output:

6