```import java.text.DecimalFormat;
import java.util.Scanner;

public class Q {
public static double equationSolver(double A, double B){
double r = 10000000000.0;
while (compute(r, B) < A){
r *= 2;
}

double low = B / (2 * Math.PI);
double high = r;
double mid = r/2;
while (Math.abs(compute(mid, B) - A) >= Math.pow(10, -25)){
if (compute(mid, B) - A >= 0){
high = mid;
}
else {
low = mid;
}
mid = (high + low) / 2;
}

return mid;
}

public static double compute(double r, double B){
return 2 * r * Math.sin(B / 2 / r);
}

public static void main (String [] args){
Scanner scan = new Scanner(System.in);

while (true){
double length = scan.nextDouble();
double tempChange = scan.nextDouble();
double coef = scan.nextDouble();

if (length < 0 && tempChange < 0 && coef < 0){
break;
}

if (tempChange == 0 || coef == 0){
System.out.println("0.000");
continue;
}

double newLength = length * (1 + tempChange * coef);

//System.out.println(length + " " + newLength);

double r = equationSolver(length, newLength);
//System.out.println(r);

double angle = newLength / r;

double result = r * (1-Math.cos(angle / 2));

result = Math.round(result * 1000d) / 1000d;

DecimalFormat formatter = new DecimalFormat("0.000");
System.out.println(formatter.format(result));
}

scan.close();
}
}```