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

Ex Input:
Sentence: 'a giraffe leaning over a fence from inside it's pasture'. Replace the letter 'n' with 'l' in the sentence.

Ex Output:
a giraffe lealilg over a felce from ilside it's pasture

Ex Input:
Sentence: 'the cargo train is headed to the next destination'. Replace the letter 'h' with 'x' in the sentence.

Ex Output:
txe cargo train is xeaded to txe next destination

Ex Input:
Sentence: 'a city square at night with buildings around it'. Replace the letter 'i' with 'y' in the sentence.

Ex Output:
a cyty square at nyght wyth buyldyngs around yt