[ncpc2025] fix broken link

Author: exoji2e

ncpc2025/call-for-problems.md

@@ -16,7 +16,7 @@ You can submit problems in two ways:
 1. By e-mailing a problem idea to head of jury Nils Gustafsson <[[email protected]](mailto:[email protected])> no later than Sunday, July 20 2025.
 2. By submitting a problem to NWERC and marking it as a simultaneous submission to NCPC. Further instructions will appear at [https://2025.nwerc.eu/](https://2025.nwerc.eu/) shortly.
 
-If you go for option 1, the following instructions apply. A problem proposal should consist of a draft of a problem statement (simple text file is fine), as well as a short description of the intended solution. Test data and a sample solution is appreciated, but not required. It should be possible to implement the intended solution with at most a few hundred lines of code and it should not take more than a couple of seconds to run. See [https://nordic.icpc.io/archive](/archive.md) for previous years' problems.
+If you go for option 1, the following instructions apply. A problem proposal should consist of a draft of a problem statement (simple text file is fine), as well as a short description of the intended solution. Test data and a sample solution is appreciated, but not required. It should be possible to implement the intended solution with at most a few hundred lines of code and it should not take more than a couple of seconds to run. See [https://nordic.icpc.io/archive](/archive) for previous years' problems.
 
 Note that if you submit a problem and it's selected you can not participate in NCPC.