#include <bits/stdc++.h>
using namespace std;

#define TRACE(x) cerr << #x << ' ' << x << endl
#define FOR(i, a, b) for (int i = (a); i < int(b); i++)
#define REP(i, n) FOR(i, 0, n)
#define _ << ' ' <<

typedef long long llint;
typedef long long ll;
typedef pair <int, int> pii;

#define fi first
#define sec second
#define pb push_back

void fail() {
  cout << -1;
  exit(0);
}

int main() {
  
  string s; cin >> s;

  int n = s.size();
  int sol = 0;
  while(true) {
    vector<int> ones;
    REP(i, n) {
      if(s[i] == '0') {
        ones.pb(i);
      }
    }

    if(ones.size() == 0) {
      break;
    }
    sol ++;

    set<int> av;
    FOR(i, 1, ones[0] + 1) {
      av.insert(i);
    }
    if(av.size() == 0) fail();

    int uz = -1;

    ones.pb(-1);

    REP(i, ones.size()) {
      set<int> nav;
      for(auto j: av) {
        if(ones[i] - j >= 0 && s[ones[i] - j] == '1') {
          nav.insert(j);
        }
      }
      
      if(nav.size() == 0) {
        uz = *av.begin();     
        break;
      }
      else {
        av = nav;
      }
    
    }


    string ns = s;

    REP(i, n) {
      if(ns[i] == '0' && s[i - uz] == '1') ns[i] = '1';
    }

    s = ns;
  }

  cout << sol << endl;
  return 0;
}