#include <bits/stdc++.h>

using namespace std;

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

  int n = s.length();
  int goal = 0;
  for (int i = 0; i < n; i++) {
    goal <<= 1;
    if (s[i] == '0') goal++;
  }

  unordered_set<int> S[2];
  int curr = 0;
  
  S[curr].insert(0);
  if (goal == 0) {
    cout << 0 << endl;
    return 0;
  }
  
  for (int d = 1; d <= n; d++) {
    // work backwards
    int prev = curr;
    curr = 1-curr;

    // no need to clear S[curr]
    for (auto s : S[prev]) {
      S[curr].insert(s);
      int mask = ((1 << d) - 1) << (n-d);
      for (int i = 0; i < n; i++) {
	S[curr].insert(s ^ mask);
	mask >>= 1;
      }
    }
    if (S[curr].count(goal) > 0) {
      cout << d << endl;
      return 0;
    }
  }

  return 0;
}