#include <bits/stdc++.h>

using namespace std;

string s;


int main(){
	cin >> s ;
	vector<int> v;
	int cnt = 0;
	for(int i = 0 ; i  < s.size();i++) {
		if(s[i] == '1') cnt ++;
		else {
			if(cnt != 0)v.push_back(cnt);
			cnt = 0 ;		
		}
	}
	if(cnt != 0)v.push_back(cnt);
	
	double res = 0 ;
	for(int i = 0 ;i < v.size();i ++ ) {
		int x = v[i];
		res += (x + 1) / 2 + (!(x & 1) ? sqrt(2) - 1 : 0); 
	}
	cout << fixed << setprecision(10) << res;
	return 0; 
}