#include <cstdio>
#include <cmath>

const double eps = 1e-8;
double x, c;
#define l ((c - x))

double m (double h) { return 0.5 * (h - sqrt (h * h + 4 * x * l)); }
double area (double h)
{
	double mm = m (h);
	double s2 = (x * x + mm * mm) * (l * l + (h - mm) * (h - mm));
	return s2;
}

int main ()
{
	double a, b, cc;
	scanf ("%lf%lf%lf", &a, &b, &cc);

	if (fabs (cc - a) > eps) { printf ("0\n"); return 0; }

	x = a;
	c = a + b + cc;

	double lf = -1000000.0, rg = 1000000.0, md;

	for (int i = 0; i < 2560; ++i)
	{
		md = (lf + rg) * 0.5;
		double a1 = area (lf), a2 = area (md), a3 = area (rg);
		if (a2 > a1) rg = md;
		else if (a2 > a3) lf = md;
		else if (a1 < a3) rg = md;
		else lf = md;
	}

	printf ("%0.4lf\n", sqrt (area (md)));

	return 0;
}

