Rio Hacks

Rio is solving a hacking problem to brush up his skills. The problem is as follows: He is given a matrix $M$ and a list $L$ of $k$ positions in the matrix $M_{ij}$. Starting from $L_0$, he must delete the number at $L_i^{th}$ position in the matrix. All the numbers following that number should come **one position back**. In the rear end of the matrix, put $-1$ at the empty position. Rio must