#include <bits/stdc++.h>

using namespace std;

double calc(int x) {
    if (!x) return 0;
    return (x + 1) / 2 + (!(x & 1) ? sqrt(2) - 1 : 0);
}

signed main() {
    string S; cin >> S;
    int n = S.size();
    double res = 0;
    for (int i = 0, z = 0; i <= n; ++i) {
        if (i != n && S[i] == '1') ++z;
        else res += calc(z), z = 0;
    }
    printf("%.12lf\n", res);
    return 0;
}