PC2021: Intermediate results, Problem 4, week 8

By 16th May 2021, there are 1053 registered participants from 71 countries (the list of countries is given below). During the first eight weeks, 43 solutions were submitted, out of which 20 had at least one correct part, a or b, see the 0-th hint.

There will be no more hints, but you’ll have time until 23:59 GMT, 15th June to submit a solution for Problem 5. I recommend doing it before 13:00 GMT, 13th June as in that case  you’ll get a feedback and will be having one more chance to correct your solution if it is not correct.

Problem 4 is now closed for submissions, the results and best solutions of Problem 4 will be published within a couple of days. The overall winners will be announced and the best solutions of Problem 5 will be published by 19th June (when the EuPhO-2021 will start).

Correct solutions for the part a of Problem 4 were submitted by:

Correct solutions for the part b were submitted by:

Participating countries: Algeria, Azerbaijan, Australia, Bangladesh, Belarus, Belgium, Bosnia and Herzegovina, Bolivia, Brazil, Bulgaria, Cambodia, Canada, China, Croatia, Czechia, Egypt, El Salvador, Estonia, Finland, Georgia, Germany, Greece, Hungary, India, Indonesia, Iran, Israel, Italy, Japan, Kazakhstan, Kenya, Korea, Kyrgyzstan, Latvia, Lebanon, Lithuania, Macedonia, Malaysia, Mexico, Moldova, Mongolia, Nepal, Nigeria, North Macedonia, Pakistan, Peru, Philippines, Poland, Romania, Russia, Saudi Arabia, Serbia, Singapore, Slovakia, Slovenia, South Africa, South Korea, Spain, Sri Lanka, Sweden, Switzerland, Syria, Taiwan, Thailand, Turkey, Turkmenistan, United Arab Emirates, United Kingdom, United States, Uzbekistan, Vietnam.