#include <bits/stdc++.h>
using namespace std;

const int N = 1e6 + 7;
double dp[N];

signed main() {
    cin.tie(0)->sync_with_stdio(0);

    dp[0] = 0; dp[1] = 1; dp[2] = sqrt(2);
    for (int i = 3; i < N; i++) {
        dp[i] = dp[i/2] + dp[(i-1)/2];
    }

    string s;
    cin >> s;
    int n = s.size();

    double ans = 0;
    int pre = -1;
    for (int i = 0; i < n; i++) {
        if (s[i] == '1') {
            if (pre == -1) pre = i;
        } else {
            if (pre != -1) ans += dp[i - pre];
            pre = -1;
        }
    }
    if (pre != -1) ans += dp[n - pre];
    cout << fixed << setprecision(10) << ans << endl;

    return 0;
}