http://lightoj.com/volume_showproblem.php?problem=1062

/*0.000s,1700KB*/

#include<bits/stdc++.h>
using namespace std;
double EPS = 1e-8;

int main()
{
	double a, b, c, j, c1, h, k, x;
	int T, cas = 0;
	scanf("%d", &T);
	while (T--)
	{
		scanf("%lf%lf%lf", &a, &b, &c);
		h = k = x = 0;
		double lo = 0, hi = max(a, b);
		while (fabs(lo - hi) > EPS)
		{
			x = (lo + hi) / 2;
			h = sqrt(a * a - x * x);
			k = sqrt(b * b - x * x);
			c1 = (k * h) / (k + h);
			if (fabs(c1 - c) <= EPS) break;
			else if (c1 > c)lo = x + EPS;
			else hi = x - EPS;
		}
		printf("Case %d: %.7f\n", ++cas, x);
	}
	return 0;
}