#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  string s;
  cin>>s;

  Int n=s.size();
  reverse(s.begin(),s.end());

  const Int INF = 1e9;
  vector<Int> dp0(n+1,INF),dp1(n+1,INF);
  dp0[0]=0;
  for(Int i=0;i<n;i++){
    chmin(dp0[i+1],dp0[i]+(s[i]!='0'));
    chmin(dp0[i+1],dp1[i]+1+(s[i]!='0'));

    chmin(dp1[i+1],dp0[i]+1+(s[i]=='0'));
    chmin(dp1[i+1],dp1[i]+(s[i]=='0'));
  }

  cout<<min(dp0[n],dp1[n]+1)<<endl;
  return 0;
}