#include <iostream>
#include <vector>
#include <queue>
#include <string>
#define PB push_back
#define F first
#define B back

using namespace std;

typedef long long int ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;

int b;

queue<pair<ll, int>> q;
string s;

int main(int argc, char const *argv[]) {
  cin>>s;
  b = s.size();

  if(s[0] == '0')
  {
    cout<<-1<<endl;
    return 0;
  }

  ll num = 0;

  for(int i = 0; i < b; i++)
  {
    num *= 2;
    num += s[i]-'0';
  }

  q.push({num, 0});

  while(1)
  {
    ll c = q.front().first;
    ll d = q.front().second;
    q.pop();
    if(c == (1<<b)-1)
    {
      cout<<d<<endl;
      return 0;
    }
    int ones = 0;
    int cb = b-1;
    while((c>>(cb))%2)
    {
      ones++;
      cb--;
    }
    for(int i = ones; i; i--)
      q.push({c|(c>>i), d+1});
  }


  return 0;
}