A binary string is monotone increasing if it consists of some number of `0`'s (possibly none), followed by some number of `1`'s (also possibly none).

You are given a binary string `s`. You can flip `s[i]` changing it from `0` to `1` or from `1` to `0`.

Return the minimum number of flips to make `s` monotone increasing.

Example 1:

    Input: s = "00110"
    Output: 1
    Explanation: We flip the last digit to get 00111.

Example 2:

    Input: s = "010110"
    Output: 2
    Explanation: We flip to get 011111, or alternatively 000111.

Example 3:

    Input: s = "00011000"
    Output: 2
    Explanation: We flip to get 00000000.

Constraints:

- `1 <= s.length <= 105`
- `s[i]` is either `'0'` or `'1'`.