题解 | #牛牛的并联电路#

import java.util.Scanner;
public class Main{
    public static void main(String[]args){
        Scanner reader=new Scanner(System.in);
        double r1=reader.nextDouble();
        double r2=reader.nextDouble();
        double r=1/r1+1/r2;
        System.out.println(1/r);
    }
}