I was going through a problem and got stuck in its sub-problem. In simple terms, the sub-problem is ---

Given an array of size n and q queries.
In each query you will get an element x and you have to return the largest index idx such that arr[idx] >= x or state that such index does not exists.

Constraints :
1 <= n,q <= 1e5
1 <= arr[i],x <= 1e9