Undo Three Times

Power users don't press undo three times — they type undo:3. 💪

You get actions — action words or undo:N (never undoing more than exists). Print the surviving actions comma-separated, or nothing.

Example:

Input: actions = ["cut", "copy", "paste", "undo:2", "glue"] Output: cut,glue

cut, copy, paste get pushed. undo:2 pops paste and copy off. Then glue gets pushed — leaving cut,glue.