I am writing a code in PL/SQL on Oracle 10g which requires a user input. I want to give a prompt for user input which I can’t to do so. It’d be great if you help!

I tried the following code, just to test if the prompt was working or not. However, the code if giving an error as "ORA-00900: invalid SQL statement". Can you please tell me where I’m going wrong?

ACCEPT x NUMBER PROMPT 'Please enter a value';
DECLARE
  a NUMBER:=&x;
BEGIN
  dbms_output.put_line(a);
END;
/