#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;
using u128 = unsigned __int128;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    std::cout << std::fixed << std::setprecision(10);
    
    std::string s;
    std::cin >> s;
    
    int i = 0;
    double ans = 0;
    while (i < s.size()) {
        i = s.find('1', i);
        if (i == -1) {
            break;
        }
        int j = s.find('0', i);
        if (j == -1) {
            j = s.size();
        }
        int len = j - i;
        i = j;
        if (len % 2 == 0) {
            ans += len / 2 - 1 + std::sqrt(2);
        } else {
            ans += (len + 1) / 2;
        }
    }
    std::cout << ans << "\n";
    
    return 0;
}