Transactional Storage Buffer

You are designing a transactional buffer for a database. The buffer supports five commands: 'PUSH x' (adds an integer x to the current scope), 'POP' (removes the last added element from the current scope), 'BEGIN' (starts a new nested transaction), 'COMMIT' (merges the current transaction's operations into the parent scope), and 'ROLLBACK' (discards all operations in the current scope and returns to the parent). If a 'POP' is called on an empty scope, ignore it. If 'COMMIT' or 'ROLLBACK' is called on the root scope, ignore it. Input consists of one command per line. Output the final state of the root scope as a space-separated sequence of integers. Example: PUSH 10 BEGIN PUSH 20 PUSH 30 POP COMMIT Output: 10 20