I Have an error in MySQL. Show me a syntaxt error in my query

I have this query in MySQL

create function is_prime(num int) returns boolean
begin
    declare cont;
    set cont = 2;

    while(cont != num) do
        if (num % cont = 0) then
            return false;
        end if;
        cont = cont + 1;
    end while;

    return true;
end//

VSCode show a syntaxt error. I have checked each line but i dont look the error.
Thanks and sorry for my english.

>Solution :

Declaration has to have a datatype

Also you forgot to Set the increase

DELIMITER //
create function is_prime(num int) returns boolean
begin
    declare cont INTEGER;
    set cont = 2;

    while(cont != num) do
        if (num % cont = 0) then
            return false;
        end if;
        SET cont := cont + 1;
    end while;

    return true;
end//