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

Ex Input:
Sentence: 'a couple walking down a sidewalk next to some graffiti'. Replace the letter 'a' with 'y' in the sentence.

Ex Output:
y couple wylking down y sidewylk next to some gryffiti

Ex Input:
Sentence: 'a no parking sign next to a car riding down a street'. Replace the letter 'g' with 'l' in the sentence.

Ex Output:
a no parkinl siln next to a car ridinl down a street

Ex Input:
Sentence: 'a mall filled with lots of stairs and a large clock'. Replace the letter 'h' with 'r' in the sentence.

Ex Output:
a mall filled witr lots of stairs and a large clock