#include<bits/stdc++.h>
#define LL long long
using namespace std;
const int N=1.1e6;
inline LL read(){
	LL x=0,ff=1;
	char c=getchar();
	while(!isdigit(c)&&c!='-') c=getchar();
	if(c=='-') c=getchar(),ff=-1;
	while(isdigit(c)) x=x*10ll+c-'0',c=getchar();
	return x*ff;
}
int n;
char c[N];
int main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	scanf("%s",c+1);
	n=strlen(c+1);
	int sum=0;
	double ans=0,val=sqrt(2.0); 
//	printf("%.8lf\n",val);
	for(int i=1;i<=n;++i){
		if(c[i]=='1')
			++sum;
		else if(sum!=0){
			if(sum&1)
				ans+=(sum+1)/2.0;
			else
				ans+=sum/2-1+val;
//			printf("%d %.8lf\n",i,ans);
			sum=0;
		}
	}
	if(sum&1)
		ans+=(sum+1)/2;
	else
		ans+=sum/2-1+val;
	printf("%.8lf\n",ans);
	return 0;
}