Hi,

I am trying to solve this problem but it is hard to find a possible approach. Could somebody help me?

Problem:

Let you have a rectangle cake. You want to divide it to N people. All of them must eat all piece of the cake and they have equally area. What is the minimum number of parallel cut you need to take.

Example:

Divide the cake for 5 people you need at least 3 cut: 2 horizontal cuts the cake into 3 parts: 2/5 and 2/5 and 1/5. Then with 1 vertical cut, the cake is divided into 6 parts: 4 piece2 1/5 and 2 pieces 1/10. Join 2 pieces 1/10, you have divided the cake equally for 5 people.

There is no limitation for N in this problem. However, I hope someone can show me an approach for 1 <= N <= 100000.

Hi all, today I found a very intesting prime sieve when I coding spoj PAGAIN: https://github.com/zobayer1/SPOJ/blob/master/PAGAIN.cpp The sieve is very fast and save memory but I can't understand what this code working:

#define ifC(n) (flag[n>>6]&(1<<((n>>1)&31)))
#define isC(n) (flag[n>>6]|=(1<<((n>>1)&31)))

Can anyone help me prove it?

Hi all, i am begin learnig how to use github. I want to creat some folders inside a repository like ftiasch github . In his "acm-icpc" repository have many folders. Example i want create folder "number theory" in "math" repository but i can only add some .txt or .cpp file in it, can anyone help me?

Hi all, I am now learning about lexicography in my school. It seem very interesting but not unusual in contests. I need your help of finding lexicography problems in any sources and I'd appreciate if you give some hints for the problem. Thank you for your help!

Hi! I'm now thinking about calculate geometric sum: 1+a+a^2+..+a^n mod m where a,m,n are 64-bit integer. I transform 1+a+a^2+...+a^n mod m=(a^(n+1)-1)/(a-1) mod m but a new problem appear: when gcd(a-1,m)>1 it seem impossible to find t such that t*(a-1) mod m=1. Any hint for this problem?

Now IOI 2012 is running the scoreboard is here And in order to view more information about a contestant you can click his/her name