#include<bits/stdc++.h>
using namespace std;
const int N=1e6+5;;
char s[N];
int n;
double solve(int n){
	double sum=0;
	for(int i=1;i<=(n+1)/2;i++){
		int res=n-(i-1);
		int x=res/i,r=res%i;
		double ans=(i-(r!=0))*sqrt(x)+sqrt(r);
		sum=max(sum,ans);
	}
	return sum;
}
int main(){
	scanf("%s",s+1);
	n=strlen(s+1);
	int p=0;
	double sum=0;
	for(int i=1;i<=n;i++)if(s[i]=='1')p++;else sum+=solve(p),p=0;
	sum+=solve(p);
	printf("%.12lf",sum);
	return 0;
}