Get String to Remove

Problem Overview

• Determine if target X can be formed from S by placing the cursor once and pressing Backspace multiple times.
• Inputs: strings S and X (X.length <= S.length); Output: the exact removed substring, or "-1" if not possible.
• Real-world context: simulates text editing where Backspace deletes characters to the left of the cursor without moving the mouse.
• This coding interview problem was asked in Onix interviews and is a common interview question.