#include <iostream>

using namespace std;

int dp[200000][2];

int main()
{
    string S;
    cin >> S;
    if (S[0] == '0')
    {
        dp[0][0] = 0;
        dp[0][1] = 1;
    }
    else
    {
        dp[0][0] = 1;
        dp[0][1] = 0;
    }
    for (int i = 1; i < S.size(); i++)
    {
        if (S[i] == '0')
        {
            dp[i][0] = min(dp[i - 1][0], min(i, dp[i - 1][1] + 3));
            dp[i][1] = dp[i - 1][1] + 1;
        }
        else
        {
            dp[i][0] = min(dp[i - 1][0] + 1, dp[i - 1][1] + 2);
            dp[i][1] = dp[i - 1][1];
        }
    }
    cout << min(dp[S.size() - 1][0], dp[S.size() - 1][0] + 2) << endl;
}