Invert And Equalize

You are given a binary string 𝑆 of length 𝑁. You can perform the following operation on it:

• Choose a continuous substring such that all of its characters are equal, and then invert the whole substring (i.e., if they were 0, change them to 1 and vice versa).

For example, suppose 𝑆=101111000. We may choose the substring 101111000 and change it to 100000000.

Find the minimum number of such operations needed to make all characters of 𝑆 equal.