#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<cassert>
#include<complex>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef pair<ll, ll> LP;
typedef vector<ll> vec;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-5;
const ld pi = acos(-1.0);

string s;
void solve() {
	cin >> s;
	int len = s.length();
	reverse(s.begin(), s.end());
	int dp[2] = { 0,mod };
	int cop[2] = { mod,mod };
	rep(i, len) {
		rep(j, 2)cop[j] = mod;
		if (s[i] == '0') {
			cop[0] = min(cop[0], dp[0]);
			cop[0] = min(cop[0], dp[1] + 1);
			cop[1] = min(cop[1], dp[1] + 1);
		}
		else {
			cop[0] = min(cop[0], dp[0] + 1);
			cop[1] = min(cop[1], dp[0] + 1);
			cop[1] = min(cop[1], dp[1]);
		}
		rep(j, 2)dp[j] = cop[j];
	}
	cout << min(dp[0], dp[1]+1) << endl;
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(50);
	//init();
	solve();

	//cout << "finish" << endl;
	//top
		return 0;
}