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

Ex Input:
Sentence: 'a small bird perched on some thin branches'. Replace the letter 'a' with 'f' in the sentence.

Ex Output:
f smfll bird perched on some thin brfnches


Ex Input:
Sentence: 'there is a purse on the floor with its contents spilled out'. Replace the letter 'd' with 'v' in the sentence.

Ex Output:
there is a purse on the floor with its contents spillev out


Ex Input:
Sentence: 'the two buddies are cross country skiing through the mountainous region'. Replace the letter 'w' with 't' in the sentence.

Ex Output:

the tto buddies are cross country skiing through the mountainous region