i'm doing this question: The equation x1 + x2 + ... + xk = n, where x1, x2, x3, ..., xk are positive integer variables satisfying the constraint: xi > = ci > 0. Given n, k,c1 ,c2 ,,…,ck, count the number of ways satisfy modulo MOD. ie: x1+x2+x3=7, c1=1, c2=2, c3=3, MOD=100, number of ways is 3. It's a normal question, i now it's is f(n-(k-sum_of_all(c))-1,n-1)%MOD but modular inverse (O(nlogn) solution) only satify when MOD is a prime number. And another O(n^2) solutions can't pass the time limit. Please give me hints or somethings, thank you senpai <3.

I found this from main page: "We have been made aware that gmail has recently stopped accepting some emails from the USACO server -- e.g., for new accounts and password resets. If this issue is affecting you, please try adding usaco@usaco.org to your gmail contacts list. If you are still having issues, please notify the contest director, Brian Dean (bcdean@clemson.edu). If you have recently received an email from the USACO server such as a password reset email or an account creation email, consider starring it, so that gmail will hopefully treat USACO emails with better priority." So, how to create new USACO account?

give a string, count how many repeating substring in this string, in another words, count substring appear >=2 times, and characters of substring can overlap. n<=1e5 Example: aaaaa, answer is 4, substrings are: a,aa,aaa,aaaa. aabaab, answer is 5, substrings are: a,b,aa,ab,aab. I only can solve it with O(n^2) solution and of course, it gives TLE. How to solve it in < O(n^2) time complexity? You can submit in here: https://www.spoj.com/PTIT/submit/PTIT015J/

here is my solution: https://mirror.codeforces.com/contest/1624/submission/144304382 for this problem: https://mirror.codeforces.com/contest/1624/problem/E I think time complexity of this solution is O(n*m) is small enough, but why this still give TLE? Thanks you for read my shi* blog.