Caesar cipher

mediumStrings20 XP

Shift every letter in s forward by k places in the alphabet, wrapping from z back to a. Keep upper/lower case, and leave anything that isn't a letter as it is. k is between 0 and 25.

Examples

Input: s = "Hello, World!", k = 3
Output: "Khoor, Zruog!"
Input: s = "xyz", k = 3
Output: "abc"

Examples use JSON: true/false/null are True/False/None in Python.