#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n) - 1; i >= 0; i--)
#define range(a) a.begin(), a.end()

using namespace std;
using ll = long long;

void chmin(int &x, int y) {
  x = min(x, y);
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  string S; cin >> S;
  const int N = S.size();
  reverse(range(S));
  constexpr int INF = 1e9;
  vector<int> dp_borrow(N + 1, INF);
  vector<int> dp_carry(N + 1, INF);
  vector<int> dp_zero(N + 1, INF);
  dp_zero[0] = 0;
  rep(i, N) {
    if (S[i] == '0') {
      chmin(dp_zero[i + 1], dp_borrow[i] + 1);
      chmin(dp_borrow[i + 1], dp_borrow[i] + 1);
      chmin(dp_zero[i + 1], dp_zero[i]);
      chmin(dp_zero[i + 1], dp_carry[i] + 1);
      chmin(dp_carry[i + 1], dp_carry[i] + 1);
    } else {
      chmin(dp_zero[i + 1], dp_borrow[i]);
      chmin(dp_zero[i + 1], dp_zero[i] + 1);
      chmin(dp_carry[i + 1], dp_zero[i] + 1);
      chmin(dp_carry[i + 1], dp_carry[i]);
      chmin(dp_zero[i + 1], dp_carry[i] + 1);
    }
  }
  cout << dp_zero[N] << endl;
}