Implementation: Data Structures

Dr Who`s Banquet

Dr. Who is organizing a banquet and will be inviting several guests. A guest is happy if he can chat with a fixed number of other guests. We assume that guests cannot talk to themselves. Help Dr. Who make all his guests happy, if possible, by organizing chats between guests.


Contains several data sets, and each data set is encoded on a line. A data set consists of n (n10000) positive integers a1, a2, … an. Each number ai (ai1000, 1in) is the number of chat partners guest i would like to have.


If you can make all the guests happy, you should post "ok". If not all the guests to be happy, you should get the message "fail". After each message should be displayed an empty string.

In the following table, an input data with 4 data sets and the associated output is shown.

Time limit 1 second
Memory limit 256 MiB
Input example #1
3 3 1 1
4 4 3 3 2 2 2
3 3 1 1
2 2 2 2
Output example #1




Source 2012 Southeastern Europe Regional Contest, Bucharest, Vinnica, October 13, Problem A