import static java.lang.Math.max;
import java.util.Scanner;
class Main
{
	public static void main (String[] args)
	{
		double ans = 0;
		Scanner scanner = new Scanner(System.in);
		double h = scanner.nextDouble();
		double w = scanner.nextDouble();
		//swapping value of two numbers without using temp variable
		if(w < h) {
			w = w + h;
			h = w - h;
			w = w - h;
		}
		ans = ( w >= 3 * h ? h : max (h / 2, w / 3) );
		System.out.printf("%.4f", ans);
	}
}
 

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