import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); String s = in.next(); int count = 0; for(int i=0;i<s.length()-1;i++){ int pre = s.charAt(i)-'0'; int suf = s.charAt(s.length()-1)-'0'; if((pre + suf) % 2 == 0){ count++; } } System.out.println(count); } }