Transform String

Chef gives you 2 strings $A$ and $B$. You can perform the following operation on $A$ as many times as you want. - Remove character $A_{i}$ from the string $A$. This has a cost of $i$ which is the index of the element that you are removing. **Note that cost is always equal to the index in current string and not the original string.** Refer to the sample test case for example. You have to print t