#include <bits/stdc++.h>

using namespace std;

const long double EPS = 0.0000001;

long double a, b;

long double s(long double x, long double y) {
    long double tmp = sqrt(x*x + y*y);
    /*if (tmp - (a + b) >= -EPS || b - (a + tmp) >= -EPS || a - (b + tmp) >= -EPS)
        return -1;
    */
    if ((a + b) - tmp >= -EPS && (a + b) - tmp <= EPS)
        return 0.5 * x * y;
    else {
        long double s1 = 0.5 * x * y;
        long double p = (tmp + a + b) / 2.0;
        if ((p * (p - a) * (p - b) * (p - tmp)) < 0)
            cout << "\n" << p << " " << a << " " << b << " " << tmp << "\n";
        long double s2 = sqrt(p * (p - a) * (p - b) * (p - tmp));
        return s1 + s2;
    }
}

long double y(long double x) {
    //long double l = EPS, r = sqrt((a + b) * (a + b) - x * x);
    long double l = 0, r = sqrt((a + b)*(a + b) - x*x);
    //cout << l << " " << r << "\n";
    while (r - l > EPS) {
        long double m1 = l + (r - l) / 3,
        m2 = r - (r - l) / 3;
        if (s(x, m1) < s(x, m2))
            l = m1;
        else
            r = m2;
    }
    //cout << x << " " << l << " " << s(x, l) << "\n";
    return s(x, l);
}

int main()
{
    freopen("1.txt", "r", stdin);
    freopen("2.txt", "w", stdout);
    cin >> a >> b;

    if (a > b)
        swap(a, b);

    long double l = 0, r = a + b;
    //cout << l << " " << r << "\n";
    while (r - l > EPS) {
        long double m1 = l + (r - l) / 3,
        m2 = r - (r - l) / 3;
        if (y(m1) < y(m2))
            l = m1;
        else
            r = m2;
    }
    cout << fixed;
    cout.precision(7);
    cout << y(l);
    return 0;
}