Dr Who`s Banquet#3841
Dr. Who is organizing a banquet and will be inviting several guests. A guest is happy if they can chat with a specific number of other guests. Note that guests cannot talk to themselves. Help Dr. Who make all his guests happy, if possible, by arranging chats between guests.
The input consists of several data sets, each described on a separate line. Each data set consists of n~(n \le 10000) positive integers a_1, a_2, \ldots, a_n. Each integer a_i~(a_i \le 1000,~1 \le i \le n) denotes the number of chat partners that guest wishes to have.
If it is possible to make all guests happy, output ok. If not all guests can be made happy, output fail. After each output, print an empty line.
Example 1