import java.io.*;
import java.util.*;

public class Magical
{
	private static final double EPS = 1.0e-6;

	private static final Scanner cin = new Scanner(System.in);

	public static void main(String[] args)
	{
		while(true) {
			double a = (double)(cin.nextInt());
			double b = (double)(cin.nextInt());
			double s = (double)(cin.nextInt());

			if(a == 0.0 && b == 0.0 && s == 0.0) { break; }

			System.out.println(doit(a, b, s) * 4.0);
		}
	}

	private static double doit(double a, double b, double s)
	{
		double hi = (a * a + b * b) / 1.0;
		double lo = (a * a + b * b) / 4.0;

		while(hi - lo >= EPS) {
			double rsq = (hi + lo) / 2.0;
			if(area(a, b, rsq) > s) { hi = rsq; } else { lo = rsq; }
		}

		return (hi + lo) / 2.0;
	}

	private static double area(double a, double b, double rsq)
	{
		double x1 = a / 1.0;
		double y1 = b / 1.0;
		double x2 = a / 2.0;
		double y2 = b / 2.0;

		double x3 = Math.sqrt(rsq - y2 * y2);
		double y3 = Math.sqrt(rsq - x2 * x2);
		double x4 = Math.sqrt(rsq - y1 * y1);
		double y4 = Math.sqrt(rsq - x1 * x1);

		double x5 = (x3 <= x1) ? x3 : x1;
		double y5 = (x3 <= x1) ? y2 : y4;
		double x6 = (y3 <= y1) ? x2 : x4;
		double y6 = (y3 <= y1) ? y3 : y1;

		double s = 0.0;

		s += Math.atan(y6 / x6) * rsq;
		s -= Math.atan(y5 / x5) * rsq;
		s -= x5 * y6 - x6 * y5;
		s += (x5 - x2) * (y6 - y2) - (x6 - x2) * (y5 - y2);
		s += x2 * (y5 - y2);
		s += y2 * (x6 - x2);

		return s * 2.0;
	}
}