p03073 AtCoder Beginner Contest 124 - Coloring Colorfully
N tiles are arranged in a row from left to right. The initial color of each tile is represented by a string S of length N.

The i-th tile from the left is painted black if the i-th character of S is `0`, and painted white if that character is `1`.

You want to repaint some of the tiles black or white, so that any two adjacent tiles have different colors.

At least how many tiles need to be repainted to satisfy the condition?

Constraints

* 1 \leq |S| \leq 10^5
* S_i is `0` or `1`.

Input

Input is given from Standard Input in the following format:


S


Output

Print the minimum number of tiles that need to be repainted to satisfy the condition.

Examples

Input

000


Output

1


Input

10010010


Output

3


Input

0


Output

0
```python
s=input();z=sum([int(s[i])==i%2 for i in range(len(s))]);print(min(z,len(s)-z))
```