#define _CRT_SECURE_NO_WARNINGS
#include<algorithm>
#include<iostream>
#include<cstring>
#include<iomanip>
#include<vector>
#include<queue>
#include<set>
using namespace std;

const int N=60;
int n,cnt,pre[N][2],suf[N][2];
char s[N];
deque<pair<int,char> >q;
pair<int,char>c[N];

inline void solve()
{
	int ans=0;
	scanf("%s",s+1);
	
	n=strlen(s+1);
	for(int i=1;i<=n;i++)
		if(s[i]=='1')ans++;
	for(int i=1;i<=n;)
	{
		int j=i;
		while(j+1<=n&&s[j+1]==s[i])j++;
		q.push_front(make_pair(j-i+1,s[i]));
		i=j+1;
	}
	if(q.size()&&q.front().second=='0')q.pop_front();
	if(q.size()&&q.back().second=='0')q.pop_back();
	if(!q.size())
	{
		puts("0");
		return;
	}
	cnt=0;
	for(auto pos:q)
		c[++cnt]=pos;
	//for(int i=1;i<=cnt;i++)
	//	cout<<c[i].first<<" "<<c[i].second<<endl;;

	for(int i=1;i<=cnt;i++)
	{
		if(c[i].second=='0')
			pre[i][0]=pre[i-1][0]+c[i].first,
			pre[i][1]=pre[i-1][1];
		else pre[i][0]=pre[i-1][0],
			pre[i][1]=pre[i-1][1]+c[i].first;
	}
	for(int i=1;i<=cnt;i++)
		for(int j=i;j<=cnt;j++)
			if(c[i].second=='1'&&c[j].second=='1')
				ans=min(ans,pre[j][0]-pre[i-1][0]+pre[i-1][1]+pre[cnt][1]-pre[j][1]);
	printf("%d\n",ans);
	for(int i=1;i<=n;i++)
		pre[i][0]=pre[i][1]=0;
}

signed main()
{
	int T;
	//scanf("%d",&T);
	T=1;
	while(T--)solve();
	return 0;
}