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1.2 KiB

Look-and-Say

Goal

Given an iteration-count generate and output the look-and-say sequence.

The sequence starts with 1. Subsequent numbers are derived by describing the previous number in terms of consecutive digits.

To generate an entry of the sequence, examine the previous entry.

Read off the digits of the previous entry, counting the number of digits in groups of the same digit.

In human terms this is like speaking out loud how often each digit appears consecutively.

Keep in mind: the output becomes very long very quickly.

Input

iterations - a numeric value how often the process is repeated

Output

The head of the generated sequence after iterating by the given input.

Constraints

  • 0 <= iterations <= 28
  • Start value = 1

Examples

  • for input 0 iterations, output 1, i.e. the starting value)
  • for input 1 iterations, output 11, i.e. reading the previous entry 1 as one 1
  • for input 2 iterations, output 21, i.e. reading the previous entry 11 as two 1s
  • for input 3 iterations, output 1211, i.e. reading the previous entry 21 as one 2 one 1
  • for input 4 iterations, output 111221, i.e. reading the previous entry 1211 as one 1 one 2 two 1