#include<bits/stdc++.h>
using namespace std;
const int N=1000005;
string s;
long double f[N],as;
signed main(){
    //  freopen("1.in","r",stdin);
    cin.tie(0),cout.tie(0),ios::sync_with_stdio(0);
    cin>>s;int n=s.length();
    int tmp=0;
    f[0]=0;f[1]=1;f[2]=sqrt(2);
    for(int i=3;i<=n;++i)
        f[i]=max(f[i-2]+1,f[i-3]+sqrt(2));
    for(int i=0;i<n;++i)if(s[i]=='1')++tmp;
    else as+=f[tmp],tmp=0;
    // cerr<<tmp<<"\n";
    as+=f[tmp];
    printf("%.10Lf",as);
    return 0;
}