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

const int N = 1000001;

char a[N];
int n;

double f[N];
void gen() {
    f[1] = 1;
    for (int i = 2; i < N; i++) {
        if (i & 1) {
            f[i] = (i + 1) / 2;
        } else {
            f[i] = sqrt(2) + (i - 2) / 2;
        }
    }
}

int main() {
    gen();
    scanf("%s", a + 1);
    n = strlen(a + 1);

    double ans = 0;
    int one = 0;
    for (int i = 1; i <= n + 1; i++) {
        if (i <= n && a[i] == '1') {
            one++;
        } else if (i == n + 1 || a[i] == '0') {
            ans += f[one];
            one = 0;
        }
    }
    printf("%.9f\n", ans);
    return 0;
}