We, HACKARZ, are glad to invite you to participate in HACKARZ FOOLS CONTEST #4, which will take place on Jun/28/2025 18:00 (Moscow time). You will be given 8 problems and 2 hours to solve them. The problems ARE NOT SORTED ACCORDING TO DIFFICULTY so please read the full problem set.

The problems were authored & prepared by: Ahmed_Salamaa, .Habiba., MohammadAbduljalil, ahmedfouadnew, Youssef_Elwazzan, Hamed5001, and the coordinator, me (Since Ahmadsm2005 is busy).

We had testers from all over the Arab region, from Morocco in the west to Palestine & Syria in the east.

We would like to thank FTS_Problem_C, benjellounelghali99, Magician_Mathematician, plankk, Metal_Sonic, Mohanad_Nahhal, NourWaelAli, Rayo, and Wawi for testing.

Special thanks to yahia, who tested and played a big role in the contest preparation to make it better.

We would like to thank our media team for their efforts — especially the leader enfp, who did a great job.

We would like to thank Maqed for his technical support in the custom standings.

Join the group: https://codeforces.me/group/zJtqriSgdw/contests.

IMPORTANT NOTES:

• Solving some problems may depend on reading others.
• Searching for anything is allowed during the contest, but using AI like ChatGPT is not allowed.