In this task, you need to replace a letter in the sentence with another given letter.

Example Input: Sentence: 'a group of people walking along a dirty snow covered road'. Replace the letter 'n' with 'i' in the sentence.
Example Output: a group of people walkiig aloig a dirty siow covered road

Example Input: Sentence: 'a group of men sitting at a desk with lap top computers'. Replace the letter 'p' with 'z' in the sentence.
Example Output: a grouz of men sitting at a desk with laz toz comzuters

Example Input: Sentence: 'a black motorcycle on the side of the road parked next to a car'. Replace the letter 'y' with 'f' in the sentence.
Example Output:
a black motorcfcle on the side of the road parked next to a car