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

Input: Consider Input: Sentence: 'flower in a vase full of water sitting on a stand '. Find frequency of the letter 'l'

Output: 3

Input: Consider Input: Sentence: 'group of snowboarders on a snowy trail overlooking a mountain'. Find frequency of the letter 'r'

Output: 5

Input: Consider Input: Sentence: 'a dog running in a field with people around'. Find frequency of the letter 'd'
Output: 3