#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using ll =  long long ;
using P = pair<int,int> ;
const int INF = 1e9;
const int MOD = 1000000007;

int main(){
    string s;
    cin >> s;
    int n = s.size();
    vector<vector<int>> dp(n+1,vector<int>(2,INF));
    dp[0][0] = 0;
    for(int i=1;i<=n;i++){
        int sd = s[n-i] - '0';
        //cout << sd  << endl;
        if(sd == 0){
            dp[i][0] = min(dp[i-1][0],dp[i-1][1] + 1);
            dp[i][1] = dp[i-1][1] + 1;
        }else{
            dp[i][0] = dp[i-1][0] + 1;
            dp[i][1] = min(dp[i-1][0] + 1,dp[i-1][1]);
        }
    }
    dp[n][1] ++;
    cout << min(dp[n][0],dp[n][1]) << endl;
    /*
    rep(i,n){
        rep(j,2) cout << dp[i][j] << " ";
        cout << endl;
    }*/
    
    return 0;
}