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

Example Input: Sentence: 'a red hydrant is sitting on the sidewalk in the city'. Replace the letter 'n' with 'r' in the sentence.
Example Output: a red hydrart is sittirg or the sidewalk ir the city

Example Input: Sentence: 'a person jumping up in the air on a snowboard'. Replace the letter 'r' with 'o' in the sentence.
Example Output: a peoson jumping up in the aio on a snowboaod

Example Input: Sentence: 'a person with a cell phone standing next to a train'. Replace the letter 's' with 't' in the sentence.
Example Output:
a perton with a cell phone ttanding next to a train