Largest Square in the garden

Chef has a garden of size $N \times N$. The garden is divided into $N^2$ squares of size $1\times 1$ each. Chef has plants in some unit squares of the garden, because of which, that part looks *green*. Formally, for the $i^{th}$ row $(0 \le i \lt N)$, Chef has plants in all the columns from $A_i$ to $B_i$ (both inclusive) where $0 \le A_i \le B_i \lt N$. Help Chef find the **length** of the s