#include"bits/stdc++.h"

using lint = int64_t;

using namespace std;

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    string s; cin>>s;
    int n = int(s.size());
    vector<int> ones(n+2), zeros(n+2);
    for(int i = 1; i <= n; i++){
        ones[i] += ones[i-1];
        zeros[i] += zeros[i-1];
        if(s[i-1] == '1') ones[i]++;
        else zeros[i]++;
    }
    ones[n+1] = ones[n];
    zeros[n+1] = zeros[n];
    int ans = min(ones.back(), zeros.back());
    for(int l = 1; l <=n; l++){
        for(int r = l; r <=n; r++){
            int cur = ones[l-1] + (zeros[r] - zeros[l-1]) + (ones.back() - ones[r]);
            ans = min(ans, cur);
        }
    }
    cout<<ans<<"\n";

    return 0;
}