\[ 012345678910{\color{blue}111}21314\ldots\]

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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