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

Input: Consider Input: Sentence: 'two zebras standing around while a third zebra drinks from a pond'. Find frequency of the letter 's'

Output: 3


Input: Consider Input: Sentence: 'the little girl is flying her kite in the field'. Find frequency of the letter 'i'

Output: 7


Input: Consider Input: Sentence: 'a man in glasses eating a donut out of a cup'. Find frequency of the letter 'a'


Output: 6