Rules
 Open Contest 2007 will consist of 10 problems. The competition will last for several days, from 15 April 2007 to 27 April 2007. Solutions to any problem can be submitted to the online judge multiple times, but not more than 256. Each solution will be executed with a set of tests. Results received by your program will be processed using a special Judge Program that will evaluate the correctness/effectiveness of your solution. In some tasks you will receive a numeric score for your solution. The score will be proportional to the efficiency of the algorithm proposed by you. This score will define your place in the rating table for a given problem. Only the best solution of each participant for a given problem will be considered in the rating tables. Current results and information about all submitted solutions will be automatically generated by the Sphere Online Judge system and will be accessible to all participants of the competition.
 All contest problems will be divided into two groups: classical and challenge. For problems of the classical type a problem is considered solved if your solution receives 'accepted' status. For problems of the challenge type a problem is considered solved if your solution receives nonzero score.
 Any person that registered in the Sphere Online Judge system can take part in the contest. Solving problems using several accounts is strictly forbidden and may result in permanent banning from the contest!

The solution to a problem can be written in any programming language supported
by Sphere Online Judge, unless additional
conditions are stipulated for a problem. The number of the sent solutions for a
specific problem is limited from above by 256 per participant. All excessive
solutions (after the 256th) are not taken into consideration in the calculation
of final statistics. The score for a particular problem is calculated using the
following formulas:
 For a problem of the classical type: table_score = nominal_task_score, where: table_score  score added to global statistics, nominal_task_score  nominal score for the problem (in some way proportional to the difficulty of the problem).
 For a problem of the challenge type: table_score = (nominal_task_score*your_score)/max_score, where: table_score  score added to global statistics, nominal_task_score  nominal score for the problem (in some way proportional to the difficulty of the problem), your_score  score received by your best solution to the problem, max_score  maximum score received by a solution to the problem, taken over all contestants. Solutions which have earned a score of zero are not taken into consideration in the calculation of statistics.
 The organizers of the contest reserve the right to make use of all submitted source code files for their own purposes (more specifically: to publish them after the contest is over).
 The organizers of the contest reserve the right to change the rules in case of need or in the event of exceptional circumstances not considered in the previous version of the rules.