Self-Improvement

Your Task

You must create a self-mutable program that, when run, outputs a non-zero integer and also overwrite the file with a program that outputs double the number.

For example, if I run the program self-improvement and it outputs 10, it must output 20 when I run it the second time, output 40 the next time, and so on.

Restrictions

• You must not rely on any file on the computer other than your program.
• Said program must consist of only one file.
• Of course, no loopholes banned from the entire site.