import java.util.Scanner;

class ML36
{
	public static void main (String[] args)
	{
		double v, u, s, t;
		double inf = Double.POSITIVE_INFINITY;
		Scanner scanner = new Scanner(System.in);
		
		v = scanner.nextDouble();
		u = scanner.nextDouble();
		s = scanner.nextDouble();
		
		t = (v>=u) ? s/(v+u) + s/(v-u) : inf;
		
		System.out.println(t);
	}
}