Basically the problem is, given array $$$A$$$ of length $$$n$$$, queries of the form

1. find $$$x$$$ : find leftmost index with $$$A_i >= x$$$

2. upd $$$i$$$ $$$y$$$ : increase $$$A_i$$$ by $$$y$$$

So we need to use a segment tree to maintain RMQ of $$$A$$$. Updates are standard. When a query comes, we first check for maximum in the interval $$$[1,n]$$$. If it's $$$< x$$$ then the ans is $$$0$$$. Otherwise check if max in $$$[1,n/2] >= x$$$. In that case we move left, otherwise we go right and query.

Complexity : $$$O(n lg n)$$$