Конь в поле

def get_knights_move_from_cells(chessboard_cells, knight_cells_set):
    res = set()
    for cell in knight_cells_set:
        x, y = cell
        res.add((x + 1, y + 2))
        res.add((x + 1, y - 2))
 
        res.add((x - 1, y + 2))
        res.add((x - 1, y - 2))
 
        res.add((x + 2, y + 1))
        res.add((x + 2, y - 1))
 
        res.add((x - 2, y + 1))
        res.add((x - 2, y - 1))
    return res & chessboard_cells
#==============================================================================
def knight_moves_count(chessboard_cells, x1, y1, x2, y2):
    knight_cell_start = (x1, y1)
    knight_cell_finish = (x2, y2)
    knight_cells_set = set()
    knight_cells_set.add(knight_cell_start)
    knight_cells_set &= chessboard_cells
 
    for k in range(1, len(chessboard_cells)):
        knight_cells_set = get_knights_move_from_cells(chessboard_cells, knight_cells_set)
        if knight_cell_finish in knight_cells_set:
            return k
#==============================================================================
def get_chessboard_cells(n):
    res = set()
    for i in range(1, n + 1):
        for j in range(1, n + 1):
            res.add((i, j))
    return res
#==============================================================================
def main():
    n = int(input('n = '))
    print()
    x1 = int(input('x1 = '))
    y1 = int(input('y1 = '))
    print()
    x2 = int(input('x2 = '))
    y2 = int(input('y2 = '))
    print()
 
    chessboard_cells = get_chessboard_cells(n)
    counter = knight_moves_count(chessboard_cells, x1, y1, x2, y2)
    print(counter)
 
main()