**Time limit:**1.00 s**Memory limit:**512 MB

*invert*it (from 0 to 1 or from 1 to 0). What is the minimum number of inversions if you act optimally?

**Input**

The only input line has a bit string of length $n$.

**Output**

Print one integer: the minimum number of inversions.

**Constraints**

- $1 \le n \le 10^6$

**Example**

Input:

`011001`

Output:

`2`

Explanation: You can invert the third and fourth bit, and the resulting string is 010101.