#include<bits/stdc++.h>
using namespace std;

int n;
char s[52];

int main(){
    scanf("%s",s+1),n=strlen(s+1);
    int answer=n;
    for(int i=1;i<=n;i++)
        for(int j=i;j<=n;j++){
            int cnt=0;
            for(int k=1;k<=n;k++)
                if(i<=k&&k<=j)cnt+=s[k]=='0';
                else cnt+=s[k]=='1';
            answer=min(answer,cnt);
        }
    int cnt=0;
    for(int k=1;k<=n;k++)cnt+=s[k]=='1';
    printf("%d\n",min(answer,cnt));
    return 0;
}