#include <bits/stdc++.h>

using namespace std;

int dp[55][3];

void solve(){
    string s; cin >> s; int n = s.size(); s = ' ' + s;
    dp[0][1] = n, dp[0][2] = n, dp[0][0] = 0;
    for (int i = 1; i <= n; ++ i){
        for (int t : {0, 1, 2}) dp[i][t] = n;
        if (s[i] == '0'){
            dp[i][0] = dp[i - 1][0];
            dp[i][2] = min(dp[i - 1][1], dp[i - 1][2]);
            dp[i][1] = dp[i - 1][1] + 1;
        }
        else {
            dp[i][0] = dp[i - 1][0] + 1;
            dp[i][1] = min(dp[i - 1][1], dp[i - 1][0]);
            dp[i][2] = dp[i - 1][2] + 1;
        }
        //for (int t : {0, 1, 2}) cout << dp[i][t] << ' ';
        //cout << '\n';
    }

    cout << min({dp[n][0], dp[n][1], dp[n][2]});
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    solve();

    return 0;
}