#include <bits/stdc++.h>

using namespace std;

#define int long long
#define fi first
#define se second
#define endl '\n'

typedef pair<int,int> PII;

void solve(){
	string s;
	cin >>s;
	int n =s.size();
	s = " " + s;
	int now = 0;
	double ans = 0;
	for(int i = 1;i <= n;i ++){
		if(s[i] == '1'){
			now ++;
		}
		else{
			if(now % 2 != 0){
				ans += ((now + 1) * 1.0) / 2.0;
			}
			else if(now){
				ans += ((now - 2) * 1.0 / 2.0) + sqrt(2);
			}
			now = 0;
		}
	}
	if(now % 2 != 0){
		ans += ((now + 1) * 1.0) / 2.0;
	}
	else if(now){
		ans += ((now - 2) * 1.0 / 2.0) + sqrt(2);
	}
	printf("%.10lf",ans);
}

signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int T;
	T = 1;
	while(T --){
		solve();
	}
}