#include "bits/stdc++.h"

using namespace std;

void solve()
{
    string s;
    cin >> s;
    int n = s.size();
    int dp[] = {0,
                10000000};
    for (int i = n - 1; i >= 0; i--)
    {
        int nx[2] = {};
        if (s[i] == '0')
        {
            nx[0] = min(dp[0], dp[1] + 1);
            nx[1] = min(dp[1] + 1, dp[0] + 2);
        }
        else
        {
            nx[0] = dp[0] + 1;
            nx[1] = min(dp[1], dp[0] + 1);
        }
        swap(dp, nx);
    }
    cout << min(dp[0], dp[1] + 1) << endl;
}

int main()
{
    solve();
    return 0;
}