Problem:
Score : 100 points

Problem Statement

In an electric circuit, when two resistors R_1 and R_2 are connected in parallel, the equivalent resistance R_3 can be derived from the following formula:

\frac{1}{R_1} + \frac{1}{R_2} = \frac{1}{R_3}

Given R_1 and R_2, find R_3.

Constraints

1 \leq R_1, R_2 \leq 100

R_1 and R_2 are integers.

Input

The input is given from Standard Input in the following format:

R_1 R_2

Output

Print the value of R_3.

The output is considered correct if the absolute or relative error is at most 10^{-6}.

Sample Input 1

2 3

Sample Output 1

1.2000000000

Sample Input 2

100 99

Sample Output 2

49.7487437186

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <tgmath.h>
#include <time.h>
#define ll long long
#define min(a, b) ((a) > (b) ? (b) : (a))
#define max(a, b) ((a) > (b) ? (a) : (b))
#define miin(a, b, c) min((a), min((b), (c)))
#define maax(a, b, c) max((a), max((b), (c)))
#define mod 1000000007

double a, b;

main()
{
    scanf("%lf%lf", &a, &b);
    printf("%.7f\n", a * b / (a + b));
    return 0;
}