A problem from December Lunchtime 2017 matches with a problem from ACM-ICPC Dhaka Site Regional Contest 2017 !

Problem Strange Function from December Lunchtime 2017 matches exactly with problem I: Repeated Digit Sum from ACM-ICPC Dhaka Site Preliminary Contest 2017 !!

Codechef Lunchtime was held on 30 December 2017.
ACM-ICPC Asia Dhaka Site Preliminary Contest was held on 23 September 2017.

Author of the problem on codechef was: abx_2109, tester: kingofnumbers

Author of the problem for ICPC Dhaka Site Preliminary was: Jane Alam Jan [Founder of LightOJ, alternate writter was: Hasnain Heickal Jami

That problem is strange function not Too Much Sweetness.


Thank you for reporting. We are investigating this.

Please tend to use the feedback thread to report all such instances as well in future. It helps in funneling information at a single place. Thank you. :slight_smile:

Also, the problem set was officially uploaded to the website of hosting university, and the link to that was also added in ACM_ICPC Baylor website.
In this link icpc page see at the right side, under check out, the problem link is given, which is: problems


The function that is asked in my problem i.e F(X) is quite an old and a popular function and is available on many websites(including wikipedia).Its called digital root. Just have a look here. From this blog 5th point I first read about this function that takes the repeated sum of the digits of a number.Here only the property F(X*X)=F(F(X)*F(X))(commonly called multiplication property of digital roots) is mentioned which I have used for my problem.This blog is way older than Dhaka regional contest september,2017.So I haven’t copied from anywhere. I hope this clears your doubt.


This is a very popular function and has been used a lot of times before as well(even i have solved qns of this type before). A very false accusation according to me.