CF gym10073G

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define test int t; cin>>t; for(int cs=1;cs<=t;cs++)
int main()
{
   ios_base::sync_with_stdio(0);
   cin.tie(0);cout.tie(0);

   string a;
   ll c,i,j,k=0,l=0;
   cin>>a;
   for(i=0;i<a.size();i++)
   {
       if(a[i]=='1') k++;
       else l++;
   }

   cout<<min(k,l)<<endl;
   return 0;
}