Message from Space

You have received an encrypted message from space. Your task is to decrypt the message with the following simple rules:

• Message string will consist of capital letters, numbers, and brackets only.
• When there's a block of code inside the brackets, such as [10AB], it means you need to repeat the letters AB for 10 times.
• Message can be embedded in multiple layers of blocks.
• Final decrypted message will only consist of capital letters.

Create a function that takes encrypted message str and returns the decrypted message.

Examples

spaceMessage("ABCD") ➞ "ABCD"

spaceMessage("AB[3CD]") ➞ "ABCDCDCD"
// "AB" = "AB"
// "[3CD]" = "CDCDCD"

spaceMessage("IF[2E]LG[5O]D") ➞ "IFEELGOOOOOD"

Notes

N/A