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

Input: Consider Input: Sentence: 'a man in a sweatshirt is taking his own picture'. Find frequency of the letter 'u'

Output: 1

Input: Consider Input: Sentence: 'people fishing and enlarge mountainlake with trees lining the shoreline'. Find frequency of the letter 't'

Output: 4

Input: Consider Input: Sentence: 'a tiled floor in a large white room'. Find frequency of the letter 'l'
Output: 3