/* -*- coding: utf-8 -*-
 *
 * 1070.cc:  No.1070 Missing a space - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100;

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

/* main */

int main() {
  scanf("%s", s);
  int n = strlen(s);

  int c = 0;
  for (int i = 1; i < n; i++)
    if (s[i] == '0') c++;

  printf("%d\n", n - 1 - c);
  return 0;
}