#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ii = pair<int,int>;
using vi = vector<int>;
using vii = vector<ii>;
using vvi = vector<vi>;
#define ALL(x) (x).begin(),(x).end()
#define ff first
#define ss second
#define D(a) cerr << ">> " << #a << " = >" << a << "<" << endl
#define PB push_back
#define F(i,a,b) for ( int i = (int)(a); i < (int)(b); ++i )
#define FD(i,a,b) for ( int i = int(a); i >= int(b); --i )
#define R1(a) scanf("%d",&a)
#define R2(a,b) scanf("%d%d",&a,&b)
#define R3(a,b,c) scanf("%d%d%d",&a,&b,&c)
#define DR1(a) int a; scanf("%d",&a)
#define DR2(a,b) int a,b; scanf("%d%d",&a,&b)
#define DR3(a,b,c) int a,b,c; scanf("%d%d%d",&a,&b,&c)

const int INF = 1e9 + 7;
constexpr const double PI = acos(-1);
const double EPS = 1e-9;

int main( ) {
    ios::sync_with_stdio(0);
    ll   n = 0;
    char c;
    cin >> c;
    if (c == '0') {
        cout << -1 << endl;
        return 0;
    }
    do {
        n = n * 2 + c - '0';
    } while (cin >> c);
    map<ll,int> dist{ { n, 0 } };
    queue<ll> q;
    q.push(n);
    while (!q.empty()) {
        auto u = q.front();
        q.pop();
        F(i,0,40) {
            auto v = u | (u >> i);
            if (dist.insert({v, dist[u] + 1}).ss) {
                q.push(v);
            }
        }
    }
    cout << dist.rbegin()->second << endl;
    return 0;
}