Shroud and string operations

Shroud's friend is a very good programmer. He gave shroud a problem to solve, in the problem you are given a string $S$ and $N$ operations have been performed on the string. Shroud needs your help to find the original string. The operation is as follows : - Assuming 1-based indexing $i$'th character from the end will be inserted between $i$'th and $i+1$'th index from the start. The string contain