Time Capsule Unpacking Order

A museum stores its recovered artifacts inside a nested system of time capsules. Every capsule either directly holds a single artifact, tagged with an integer id, or holds a bundle of smaller sub-capsules, each of which follows this very same rule. Given the complete nesting structure of one shipment, determine the order in which artifact tags would be read out if every capsule in the shipment were opened and unpacked, left to right, depth first.

Input format

A single line containing one string that describes the shipment as a bracketed literal:

• The shipment itself is always written as [ element , element , ... ] (it may be empty: []).
• Each element is either an integer (optionally prefixed with -), representing a single artifact tag, or a nested capsule written using this same bracketed literal grammar ([...]), which itself contains zero or more further elements.
• The literal contains no whitespace.

Output format

Print the artifact tags encountered during a left-to-right, depth-first unpacking of the shipment, separated by single spaces, in the order they appear once every capsule is fully opened. If the shipment holds no artifacts at all, print an empty line.

Constraints

• The literal's length is between 2 and 20000 characters.
• The nesting depth of capsules is at most 50.
• The shipment contains between 0 and 1000 artifact tags in total.
• Each artifact tag satisfies -10^6 <= tag <= 10^6.

[1,[2,[3,4],5],6]

1 2 3 4 5 6

[-3,[],[7,[-8,9]]]

-3 7 -8 9