# 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.

#### Input

Contains several data sets, and each data set is encoded on a line. A data set consists of **n** (**n** ≤ **10000**) positive integers `a`

, _{1}`a`

, … _{2}`a`

. Each number _{n}`a`

(_{i}`a`

≤ _{i}**1000**, **1** ≤ **i** ≤ **n**) is the number of chat partners guest **i** would like to have.

#### Output

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.

3 3 1 1 4 4 3 3 2 2 2 3 3 1 1 2 2 2 2

fail ok fail ok