#include <iostream>
using namespace std;

int main() {

string ch;
int a[200];
int b[200];
int n,i,t,res;
cin >> ch;
n= ch.length();
for (i =0; i< 200; i++)
b[i]= 0;
for(i=1; i<=n; i++) {
a[i] = ch[i-1]-'0';
b[i] = b[i- 1] + a[i];
}
res= b[n];
t=0;
for(i=n; i>0; i--) {
if (a[i]== 0)
t++;
if (b[i- 1] +t < res)
res=b[i-1]+t;
}
cout << res << endl;
return 0;
}

输入: 1001101011001101101011110001
输出：11