• 92

## Learning Opportunities

This puzzle can be solved using the following concepts. Practice using these concepts and improve your skills.

## Goal

Given an element of the Look-and-say series, you must walk the series in the reverse direction until you find the first valid element of the series.

The Look-and-say series transforms a given number by changing a "spoken" interpretation of that number into a numerical format. The spoken interpretation of a number takes groups of digits and states the count of repeated digits in each group.

13112221 =>    1  3  11  222  1 =>        "One 1, one 3, two 1s, three 2s, one 1" =>            11  13  21  32  11 =>                1113213211

Given the above example of the Look-and-say series, if you were given "1113213211" as an input, the first step in walking the series in reverse would yield "13112221". Be careful after each iteration because the process is not always reversible...

For example:

1211 =>     1 x "2" + 1 x "1" = 21 =>         2 x "1" = 11 =>             1 x "1" = 1. This is the last possible step

41 =>     4 x "1" = 1111 =>         1 x "1" + 1 x "1" = 11. This step is not reversible!The solution is 1111

You can find detailed information of this sequence in https://en.wikipedia.org/wiki/Look-and-say_sequence.
Input
Line 1: An integer n for the starting element of the series.
Output
Line 1 : The very first valid element of the look-and-say series.
Constraints
Log(n) < 100
Example
Input
1211
Output
1

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