Problem:
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

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
 
public class Main {
        public static void main(String[] 麺類総選挙){
            Scanner うどん = new Scanner(System.in);
            String そば = うどん.nextLine();
            int ラーメン = そば.length();
            String 山菜そば[] = そば.split("");
            String[] シチュー = new String[ラーメン];
            String[] 信州そば = new String[ラーメン];
            for(int 稲庭うどん=0;稲庭うどん<ラーメン;稲庭うどん++) {
                シチュー[稲庭うどん] = String.valueOf((稲庭うどん + 1)%2); //白スタート
                信州そば[稲庭うどん] = String.valueOf((稲庭うどん)%2);
            }
            //差分比較
            int 赤いきつね=0;
            int 緑のたぬき=0;
            for(int スパゲッティ=0;スパゲッティ<ラーメン;スパゲッティ++){
                if(!山菜そば[スパゲッティ].equals(シチュー[スパゲッティ])){
                    赤いきつね++;
                }else if(!山菜そば[スパゲッティ].equals(信州そば[スパゲッティ])){
                    緑のたぬき++;
                }
            }
            int 第三回人気投票;
            if (赤いきつね < 緑のたぬき) {
                第三回人気投票 = 赤いきつね;
            }else{
                第三回人気投票 = 緑のたぬき;
            }
            System.out.println(第三回人気投票);
        }
 
}