import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String input = sc.nextLine();
        System.out.println(countGoodSubstrings(input));
    }

    public static int countGoodSubstrings(String input) {
        int count = 0;
        for (int i = 0; i < input.length(); i++) {
            if (input.charAt(i) == '0') {
                for (int j = i + 1; j < input.length(); j++) {
                    if (input.charAt(j) == '1') {
                        count++;
                    } else {
                        break;
                    }
                }
            } else {
                for (int j = i + 1; j < input.length(); j++) {
                    if (input.charAt(j) == '0') {
                        count++;
                    } else {
                        break;
                    }
                }
            }
        }
        return count;
    }
}