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

#define int long long  

signed main() {  
    ios::sync_with_stdio(false);
    cin.tie(nullptr);  

	string s;
	cin >> s;

	double ans = 0;
	s += '0';

	auto calc = [&](int len) -> double {
		if (len == 0) {
			return 0.;
		}
		if (len % 2) {
			return (len + 1) / 2;
		} else {
			return len / 2 - 1 + sqrt(2);
		}
	};

	int t = 0;
	for (auto c : s) {
		if (c == '1') {
			t++;
		} else {
			ans += calc(t);
			t = 0;
		}
	} 

	cout << fixed << setprecision(10);
	cout << ans << "\n";

    return 0;
}