Python 3 please

Exercise 2. Caesar's Ciphers II Write a function decodeCipher(word, num) that takes a cipher string (of only lower case letters) and a number, and returns the decoded string that is created when every character is replaced by its mapping. For example, decodeCipher("cde", 2) should return "abc". Use this function to decode "jbj fpurzr vf terng" given that the letters had been shifted by 13. Exercise 3. Colored polygons. Write a function cpolygon(n, size) that takes in two arguments: n (the number of sides of a polygon), and size (its side length in pixels). The function draws an n-sided polygon with alternating black and red colors. Hint: The function turtle.color(col) changes the color of the pen to col, which is a string specifying the desired color (black, red, etc.)