// Author: Chuanhua Yu
// Time: 2024-11-26.
#include<bits/stdc++.h>
using namespace std;
using ll = long long;

string s;
double sq2 = sqrt(double(2));

void solve(){
    cin >> s;
    s = s + '0';
    vector<int> cnt;
    int cc = 0;
    for(auto c : s) {
        if(c == '0'){
            if(cc) cnt.push_back(cc);
            cc = 0;
        }
        else cc++;
    }
    double ans = 0;
    for(auto c : cnt){
        if(c & 1) ans += c / 2 + 1;
        else if (c == 2) ans += sq2;
        else ans += sq2 + (c - 2) / 2;
    }
    cout << fixed << setprecision(12) << ans << '\n';
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
//    int T; cin >> T;
//    while(T--)
    solve();
    return 0;
}