Update src/others/pells_equation.md

Bhaskar1312 · adamant-pwn · Bhaskar1312 · commit 36deb906b1ac · 2025-04-19T08:13:34.000+05:30
Co-authored-by: Oleksandr Kulkov &lt;adamant.pwn@gmail.com&gt;
diff --git a/src/others/pells_equation.md b/src/others/pells_equation.md
@@ -191,7 +191,7 @@ pair<long long, long long> chakravala(int n) {
 - [Pell's equation - Wikipedia](https://en.wikipedia.org/wiki/Pell%27s_equation)
 - [Periodic Continued Fractions](https://en.wikipedia.org/wiki/Periodic_continued_fraction)
 - [Chakravala Method](http://publications.azimpremjifoundation.org/1630/1/3_The%20Chakravala%20Method.pdf)
-- [Codeforces Pell's Equation](https://codeforces.com/topic/116937/en20)
+- [Pythagorean triples and Pell's equations - Codeforces](https://codeforces.com/blog/entry/116313)
 
 ## Problems
 - [Project Euler 66](https://projecteuler.net/problem=66)
