Crazy Bishops on Chessboard

Chef has a matrix of size $N\times N$. There are $N$ [bishops](https://en.wikipedia.org/wiki/Bishop_(chess)) placed on the matrix, in a zig-zag fashion, at the cells $(1, 1), (2, 2), (1, 3), (2, 4), (1, 5), \dots,$ and so on. For example, for $N = 4$, the matrix looks like: Your task is to determine the **minimum** number of moves required to reach a position where each cell $(i, i)$ contains ex