#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream>
#include <random>
#include<map>
#include <iomanip>
#include <time.h>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
#include <cassert>
#include<fstream>
#include <unordered_map>
#include <cstdlib>
#include <complex>
#include <cctype>
#include <bitset>
using namespace std;
typedef string::const_iterator State;
#define Ma_PI 3.141592653589793
#define eps 1e-5
#define LONG_INF 1e18
#define GOLD 1.61803398874989484820458
#define MAX_MOD 1000000007LL
#define MOD 998244353LL
#define seg_size 262144*4
#define REP(a,b) for(long long a = 0;a < b;++a)
long long dp[300000][2] = {};
int main(){
	string s;
	cin >> s;
	reverse(s.begin(), s.end());
	REP(q, 300000) {
		dp[q][0] = 1e9;
		dp[q][1] = 1e9;
	}
	dp[0][0] = 0;
	for (int i = 0; i < s.length(); ++i) {
		REP(q, 2) {
			int summer = q;
			if (s[i] == '1') {
				summer++;
			}
			if (summer == 2) {
				//always kuriage
				dp[i + 1][1] = min(dp[i + 1][1], dp[i][q]);
			}
			else if (summer == 1) {
				//kuriage
				dp[i + 1][1] = min(dp[i + 1][1], dp[i][q] + 1);
				//kuriagenai
				dp[i + 1][0] = min(dp[i + 1][0], dp[i][q] + 1);
			}
			else {
				//summer = 0
				dp[i + 1][0] = min(dp[i + 1][0], dp[i][q]);
			}
		}
	}
	cout << min(dp[s.length()][0], dp[s.length()][1] + 1) << endl;

}