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

Input: Consider Input: Sentence: 'a group of three dogs laying on a kitchen floor'. Find frequency of the letter 'r'

Output: 3


Input: Consider Input: Sentence: 'a woman is looking at sheep off in a field'. Find frequency of the letter 'm'

Output: 1


Input: Consider Input: Sentence: 'when the pasture is covered with snow, these sheep eat hay'. Find frequency of the letter 'v'


Output: 1