WTF, lol, How is this problem 2000 difficulty? https://codeforces.me/problemset/problem/1919/H

Let $$$m$$$ be some positive integer (not necessary prime) . There is a way to calculate $$$\displaystyle{\frac{a}{b}}\%m$$$ when b is not very big and $$$a \% b = 0$$$ Firstly, let's notice, that $$$\displaystyle{\frac{a}{b}}=mk+(a/b)\%m$$$, for some integer value k. Now, let's do some mathematical stuff:

So, the answer is $$$(a\%mb)/b$$$

Hi Guys, Can anyone help me solve this problem?

https://acm.timus.ru/problem.aspx?space=1&num=2019&locale=en

I tried to solve it greedily. Also i tried to solve it using dynamic programming. I had dp[l][r] true if exists k such that dp[l][k] is true and dp[k + 1][r] is true or dp[l + k][r — k] is true and we can connect letters from range (l, l + k) to the letters from range (r — k, r). Unfortunately, that works for O(n^3)