166
rbbbbbbbbbbbbrbrrbbrbbbrbbbbbbbbbbrbbbbbbrbbbrbbbbbrbbbbbbbrbbbbbbbrbbrbbbbbbbbrbbbbbbbbbbbbbbrrbbbrbbbbbbbbbbbbbbrbrbbbbbbbbbbbrbbbbbbbbbbbbbbrbbbbbbbbbbbbbbbbbbbbbb
 7
rrbrbrb
 1
r
 2
bb
 18
rrrrrrrrrrrrrrrrrb
 8
rbbrbrbr
 1
b
 13
rbbbrbrrbrrbb
 100
brbbbrrrbbrbrbbrbbrbbbbrbbrrbbbrrbbbbrbrbbbbbbbbbbbbbbbbrrrrbbbbrrrbbbbbbbrbrrbrbbbbrrrbbbbrbbrbbbrb
 2
rb
 2
rr
 2
br

70
 1
 0
 1
 8
 1
 0
 3
 34
 0
 1
 0

import java.util.Scanner;

public class CodeForce {
private static int r,b;
    
    public static void main(String[] args) {
    
        Scanner in=new Scanner (System.in);
        String name=in.next();
  
        char lastLetter=name.charAt(0);
     
        for(int i=1;i<name.length();++i){
            char thisLetter=name.charAt(i);
            if(lastLetter==thisLetter){
                if(thisLetter=='r'){
                    lastLetter='b';
                    ++r;
                }
                else{
                    lastLetter='r';
                    ++b;
                }
            }
            else{
                lastLetter=thisLetter;
            }
         
        }
        int answer=Math.max(r, b);
        System.out.println(answer);
        
    }
    
}
