#include <bits/stdc++.h>
#define rep(i, a, b) for(int i = (a); i <= (b); i ++)
#define nrep(i, a, b) for(int i = (a); i >= (b); i --)
using namespace std;

void print() { cerr << endl; }
template<typename T, typename ...Ts>
void print(T v, Ts ...vs) { cerr << v << " "; print(vs...); }


typedef long long ll;
ll read() {
    ll x = 0, f = 1; char ch = getchar();
    while(!isdigit(ch)) { if(ch == '-') f = -1; ch = getchar(); }
    while(isdigit(ch)) { x = (x << 1) + (x << 3) + (ch ^ 48), ch = getchar(); }
    return x * f;
}

const int N = 1e6 + 10;
char s[N];

int main() {
	scanf("%s", s + 1);
	int n = strlen(s + 1);
	int mn = 1e9;
	rep(l, 1, n) rep(r, 1, n) {
		if(l > r + 1) continue;
		int cnt = 0;
		rep(i, 1, n) {
			if(i >= l && i <= r) {
				if(s[i] == '0') cnt ++;
			} else if(s[i] == '1') cnt ++;
		}
		mn = min(mn, cnt);
	}
	cout << mn << endl;
}