#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cassert>
#include <cstdint>
#include <iostream>
#include <iomanip>
#include <string>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <bitset>

using namespace std;

using ll =  long long;
using Pll = pair<ll, ll>;
using Pii = pair<int, int>;

constexpr ll MOD = 1000000007;
constexpr long double EPS = 1e-10;
constexpr int dyx[4][2] = {
    { 0, 1}, {-1, 0}, {0,-1}, {1, 0}
};

int main() {
    std::ios::sync_with_stdio(false); cin.tie(nullptr);
    string s;
    cin >> s;
    int n  = s.length();
    vector<int> a(n+1, 0), ones(n+1, 0);
    for(int i=0;i<n;++i) a[i] = s[n-1-i] - '0';
    ones[0] = a[0];
    for(int i=1;i<n;++i) {
        ones[i] = ones[i-1] + a[i];
    }
    ones[n] = ones[n-1];

    vector<vector<int>> dp(n+1, vector<int>(2, 0));
    dp[0][0] = a[0];
    dp[0][1] = 1-a[0];
    for(int i=1;i<=n;++i) {
        if(a[i]) {
            dp[i][0] = dp[i-1][0] + 1;
            dp[i][1] = min(dp[i-1][0], dp[i-1][1]);
        } else {
            dp[i][0] = min(dp[i-1][0], dp[i-1][1] + 2);
            dp[i][1] = min(dp[i-1][0], dp[i-1][1]) + 1;
        }
    //     cerr << i << ": " << dp[i][0] << ", " << dp[i][1] << endl;
    }

    cout << dp[n][0] << endl;

}