#include<bits/stdc++.h>
#include <iostream>
#include <algorithm>
#define ll long long
#define ld long double

using namespace std;

string str;
int len,ct;
ld ans;

int main()
{
	cin >> str;
	str = str + '0';
	len = str.length();
	for(int i = 0 ; i < len ; i++)
	{
		if(str[i] == '0' && ct != 0)
		{
			if(ct % 2 == 0) 
			{
				ans = ans + sqrt(2) + ct / 2 - 1;
				ct = 0;
			}
			else 
			{
				ans = ans + (ct + 1) / 2;
				ct = 0;
			}
		}
		if(str[i] == '1') ct++;
	}
	cout << ans;
	return 0;
}