백준 1439

package baekjoon.그리디;

import java.io.BufferedReader;
import java.io.InputStreamReader;

class Main1439 {

   public static void main(String[] args) throws Exception {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String S = br.readLine();
      int zero =0, one = 0;
      char c = ' ';
      for (int i = 0; i < S.length(); i++) {
         if (c != S.charAt(i)) {
            c = S.charAt(i);
            if (c == '0') {
               zero++;
            } else {
               one++;
            }
         }
      }
      System.out.println(Math.min(zero, one));
   }
}