#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using pii=pair<int,int>;
constexpr int INF=0x3f3f3f3f;
constexpr int MXN=1e6+5;

int dp[55][55];

void solve()
{
    string s;
    cin >> s;
    int n = s.size();
    s = " " + s;
    int cnt1 = 0;
    memset(dp, -1, sizeof(dp));
    dp[0][0] = 0;
    for(int i = 1; i <= n; i ++)
    {
        if(s[i] == '0') {
//        	cout << "null : ";
            for(int j = 0; j < i; j ++) if(dp[i - 1][j] != -1)
                dp[i][j] = dp[i - 1][j];
                
//            for(int j = 0; j <= i; j ++) cout << dp[i][j] << ' ';
//        		cout << "\n\n";
            continue;
        }
        
        dp[i][i] = cnt1;
        ++ cnt1;
        dp[i][0] = cnt1;

        // save 1
        for(int j = 1; j < i; j ++) if(dp[i - 1][j] != -1) {
            dp[i][i] = min(dp[i][i], dp[i - 1][j] + i - j - 1);
        }

        // erase 1
        for(int j = 0; j < i; j ++) if(dp[i - 1][j] != -1) {
            if(dp[i][j] != -1) dp[i][j] = min(dp[i][j], dp[i - 1][j] + 1);
            else dp[i][j] = dp[i - 1][j] + 1;
        }
        
//        for(int j = 0; j <= i; j ++) cout << dp[i][j] << ' ';
//        cout << "\n\n";
    }
    int ans = n;
    for(int i = 0; i <= n; i ++) if(dp[n][i] != -1) ans = min(ans, dp[n][i]);
    cout << ans << "\n";
}
int main()
{
    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int _=1;
    // cin>>_;
    while(_--)
        solve();
    return 0;
}