A knight and a pawn are on a chess board. Can you figure out the minimum number of moves required for the knight to travel to the same position of the pawn? On a single move, the knight can move in an "L" shape; two spaces in any direction, then one space in a perpendicular direction. This means that on a single move, a knight has eight possible positions it can move to.

Write a function, knight_attack, that takes in 5 arguments:

n, kr, kc, pr, pc

n = the length of the chess board
kr = the starting row of the knight
kc = the starting column of the knight
pr = the row of the pawn
pc = the column of the pawn

The function should return a number representing the minimum number of moves required for the knight to land on top of the pawn. The knight cannot move out-of-bounds of the board. You can assume that rows and columns are 0-indexed. This means that if n = 8, there are 8 rows and 8 columns numbered 0 to 7. If it is not possible for the knight to attack the pawn, then return None.

knight_attack(8, 1, 1, 2, 2) # -> 2

knight_attack(8, 1, 1, 2, 3) # -> 1

knight_attack(8, 0, 3, 4, 2) # -> 3

knight_attack(8, 0, 3, 5, 2) # -> 4

knight_attack(24, 4, 7, 19, 20) # -> 10

knight_attack(100, 21, 10, 0, 0) # -> 11

knight_attack(3, 0, 0, 1, 2) # -> 1

knight_attack(3, 0, 0, 1, 1) # -> None