#include<cmath>
#include<cstdio>
#include<vector>
#include<cstring>
#include<iostream>
#include<algorithm>
#define fi first
#define se second
using namespace std;
typedef long long LL;
typedef pair<int,int> PII;
char s[1000009];
void solve(){
	scanf("%s",s+1); int n=strlen(s+1);
	double res=0;
	for(int i=1;i<=n;i++) if(s[i]=='1'){
		int j=i;
		while(j+1<=n&&s[j+1]==s[i]) j++;
	int l=j-i+1;
	if(l<=2) res+=sqrt(l);
	else if(l&1) res+=l+1>>1;
	else res+=(l-2>>1)+sqrt(2);
		i=j;
	}
	printf("%.9lf\n",res);
}
int main(){
	int T=1;
	// scanf("%d",&T);
	while(T--) solve();
	return 0;
}