#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("-Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-funroll-all-loops,-fpeel-loops,-funswitch-loops")
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
const long long MOD = 1e9 + 7, OO = 1e18;
const double PI = acos(-1);
const int N = 1e6 + 5;
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};

long long n, carry, ans;
string num;

int main() {
    IO
    cin >> num;
    n = num.size() - 1;
    for (int i = n; i > 0; i--)
    {
        if (num[i] == '0' && carry == 1)
        {
            ans += 2;
        }
        else if (num[i] == '1' && carry == 0)
        {
            ans += 2;
            carry = 1;
        }
        else if (num[i] == '0' && carry == 0)
        {
            ans++;
        }
        else if (num[i] == '1' && carry == 1)
        {
            ans++;
            carry = 1;
        }
    }
    if (carry == 1)ans++;
    cout << ans;
    return 0;
}