Duplicate entry for key "PRIMARY" in MySQL

Query for creating table :

create table if not exists person ( 
roll_no int(4) AUTO_INCREMENT primary key,
name varchar(25),  
city varchar(25));

Query to set start number for auto-increment primary key :

alter table person auto_increment = 1;

Query to insert data :

insert into person (name,city) values("Maxwell", "Pune");
insert into person (name,city) values("Baldwin", "Bengaluru");
insert into person (name,city) values("Novartis", "Paris");
insert into person (name,city) values("Shaun", "Mumbai");
insert into person (name,city) values("Beckham", "Toronto");
insert into person (name,city) values("Ashish", "Bengaluru");
insert into person (name,city) values("David", "Paris");
insert into person (name,city) values("PK", "London");
insert into person (name,city) values("Chris", "Bengaluru");
insert into person (name,city) values("Aston", "Mumbai");

Query to delete the row :

delete from person where roll_no=5;

Table structure after deleting the row:

roll_no      name       city
1            Maxwell    Pune
2            Baldwin    Bengaluru
3            Novartis   Paris
4            Shaun      Mumbai
6            Ashish     Bengaluru
7            David      Paris
8            PK         London
9            Chris      Bengaluru
10           Aston      Mumbai

Now, while looking to reinstate the deleted row, the compiler is throwing error as " Duplicate entry '5' for key 'PRIMARY' "

Query used to re-instate the deleted row.

update person set roll_no = roll_no + 1 where roll_no >=4 order by roll_no desc;
insert into person (roll_no, name, city) VALUES (5, "Beckham", "Toronto");

What could be the possible reason for this issue ? Any inputs would be highly recommended.