Pair Making Problem

Given an integer array $A$ of length $N$, and an **odd** integer $M$, let $f(A)$ denote the number of ordered pairs $(i, j)$ such that $1 \le i < j \le N$ and $A_i + A_j = M$. You are also given a parameter $K$, and want to make $f(A) \ge K$. Find the minimum number of array replacements you need to perform to make $f(A) \ge K$. Formally, in one replacement, you choose an index $X$, an integer