#include<bits/stdc++.h>
using namespace std;
#define inf INT_MAX
#define INF LLONG_MAX
#define ll long long
#define ull unsigned long long
#define M (int)(1e9+7)
#define P pair<int,int>
#define PLL pair<ll,ll>
#define FOR(i,m,n) for(int i=(int)m;i<(int)n;i++)
#define RFOR(i,m,n) for(int i=(int)m;i>=(int)n;i--)
#define rep(i,n) FOR(i,0,n)
#define rrep(i,n) RFOR(i,n,0)
#define all(a) a.begin(),a.end()
#define IN(a,n) rep(i,n){ cin>>a[i]; }
const int vx[4] = {0,1,0,-1};
const int vy[4] = {1,0,-1,0};
#define PI 3.14159265
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define int ll
#define vi vector<int>
#define IP pair<int,P>
#define PP pair<P,P>
#define Yes(f){cout<<(f?"Yes":"No")<<endl;}
#define YES(f){cout<<(f?"YES":"NO")<<endl;}


signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<fixed<<setprecision(20);

  string s;
  cin>>s;
  reverse(all(s));
  s.PB('0');

  int dp[210000][2];

  

  rep(i,s.size()+1){
    rep(j,2){
      dp[i][j]=inf;
    }
  }

  dp[0][0]=0;
  rep(i,s.size()){
    //cout<<s[i]<<endl;
    rep(j,2){
      if(j==0&&s[i]=='0') dp[i+1][0]=min(dp[i+1][0],dp[i][0]);
      if(j==1&&s[i]=='0'||j==0&&s[i]=='1'){
        dp[i+1][1]=min(dp[i+1][1],dp[i][j]+1);
        dp[i+1][0]=min(dp[i+1][0],dp[i][j]+1);
      }
      if(j==1&&s[i]=='1'){
        dp[i+1][1]=min(dp[i+1][1],dp[i][j]);
      }
    }
  }

  rep(i,s.size()){
    //cout<<dp[i][0]<<' '<<dp[i][1]<<endl;
  }

  cout<<min(dp[s.size()][0],dp[s.size()][1])<<endl;

}