#include <bits/stdc++.h>

#define rep(i, j, k) for (int i = (j); i <= (k); ++i)
#define per(i, j, k) for (int i = (j); i >= (k); --i)
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second
using ll = long long;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;

template<class T>inline void chkmn(T &x, T y) { if (y < x) x = y; }
template<class T>inline void chkmx(T &x, T y) { if (y > x) x = y; }

using namespace std;

int n;
string str;

int main() {
  cin.tie(nullptr) -> ios::sync_with_stdio(false);
  cin >> str, n = str.length();
  double ans = 0;
  for (int l = 0, r; l < n; l = r + 1) {
    r = l;
    if (str[l] == '0') continue;
    while (r + 1 < n && str[r + 1] == '1') r++;
    if ((r - l) & 1) {
      ans += (r - l - 1) / 2 + sqrt(2);
    } else {
      ans += (r - l + 2) / 2;
    }
  }
  cout << fixed << setprecision(9) << ans << '\n';
}