#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <stdio.h>
using namespace std;
#define int long long
int MOD = 1000000007;
void amin(int &a, const int &b) {
	a = min(a, b);
}
signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	string S;
	cin >> S;
	int N = S.size();
	int INF = (int)1 << 60;
	vector<vector<int> > dp(N + 1, vector<int>(2, INF));
	dp[0][0] = 0;

	for (int i = 0; i < N; i++) {
		if (S[N - i - 1] == '0') {
			amin(dp[i + 1][0], dp[i][0]);
			amin(dp[i + 1][1], dp[i][1] + 1);
			amin(dp[i + 1][0], dp[i][1] + 1);
		}
		else {
			amin(dp[i + 1][1], dp[i][0] + 1);
			amin(dp[i + 1][0], dp[i][0] + 1);
			amin(dp[i + 1][1], dp[i][1]);
		}
	}

	cout << min(dp[N][0], dp[N][1] + 1) << endl;
}