Contest Duration: - (local time) (100 minutes) Back to Home
C - Coloring Colorfully /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 問題文

あなたは、いくつかのタイルを黒色または白色に塗り替えることで、どの隣り合う 2 枚のタイルも異なる色で塗られているようにしたいです。

### 制約

• 1 \leq |S| \leq 10^5
• S_i0 または 1 である。

### 入力

S


### 入力例 1

000


### 出力例 1

1


### 入力例 2

10010010


### 出力例 2

3


### 入力例 3

0


### 出力例 3

0


Score : 300 points

### Problem Statement

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.

### Sample Input 1

000


### Sample Output 1

1


The condition can be satisfied by repainting the middle tile white.

### Sample Input 2

10010010


### Sample Output 2

3


### Sample Input 3

0


### Sample Output 3

0