You are given a binary string .
You have to split into one or more non-empty contiguous substrings. Each character of must belong to exactly one substring.
For a binary string , define as the smallest non-negative integer that does not appear in as a digit. For example, , , and .
After choosing a split, write the values of of the substrings from left to right, without spaces. This gives a string of digits.
Find the lexicographically smallest string that can be obtained.
We use the usual definition of lexicographic order: if one string is a proper prefix of the other, the shorter string is smaller.