MySQL - Autoincrement does not increment sequentally if last row was deleted

Question

I have a table which contains an auto incremented primary key id. If I delete the last row (highest id, for exampe id = 6) and insert a new row, the new id starts at 7. Which paramater I have to change that the primary key starts at 6?

CREATE TABLE animals (
 id MEDIUMINT NOT NULL AUTO_INCREMENT,
 name CHAR(30) NOT NULL,
 PRIMARY KEY (id)
) ENGINE=MyISAM;

INSERT INTO animals (name) VALUES
('dog'),('cat'),('penguin'),
('lax'),('whale'),('ostrich');

Result:
id name
1 dog
2 cat
3 penguin
4 lax
5 whale
6 ostrich

DELETE FROM animals WHERE id = 6;
INSERT INTO animals (name) VALUES
('x');

Result:
id name
1 dog
2 cat
3 penguin
4 lax
5 whale
7 x

Thanks for advice.