Compress the Digits X44100

Statement

Write a function $compress(n)$ that, given a positive integer $n$ , returns the number obtained by deleting from $n$ all digits (non-negative integers less than 10) that repeat the digit at their left.

Observation

All integers are assumed written in the usual base 10.

Sample session

>>> compress(1234)
1234
>>> compress(12234441)
12341
>>> compress(3)
3
>>> compress(11200000013333)
12013

Information

Author: Jordi Delgado \& José Luis Balcázar
Language: English
Official solutions: Python
User solutions: Python