# Where are they hiding ?

$012345678910{\color{blue}111}21314\ldots$

The above is the beginning of all non-negative integers concatenated into a single infinite string.

$$\color{blue}111$$ is the first sub-string with 3 identical digits in a row, with different digits preceding and following the run of the identical digits. The first $$\color{blue}1$$ of $$\color{blue}111$$ comes at position 13 (from left) in the infinite string.

Where is the first such sub-string with 4 identical digits?

Give the position of the first digit of the four.

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