PROGRAMMING:Calculate the resistance value of parallel resistance
###Task description
For the resistances R1 and R2, the parallel resistance formula is as follows:
R = 1/(1/r1 + 1/r2)
###Input format:
Two resistance impedance size, floating-point type, separated by a space.
###Output format:
The impedance value after parallel connection is 2 decimal places
###Input example:
```in
1 2
```
###Output example:
```out
zero point six seven
```
###Tips
The calculation process uses the float type.
Note: this topic is selected from openjudge website http://noi.openjudge.cn/ch0103/10/ .
answer：If there is no answer, please comment
For the resistances R1 and R2, the parallel resistance formula is as follows:
R = 1/(1/r1 + 1/r2)
###Input format:
Two resistance impedance size, floating-point type, separated by a space.
###Output format:
The impedance value after parallel connection is 2 decimal places
###Input example:
```in
1 2
```
###Output example:
```out
zero point six seven
```
###Tips
The calculation process uses the float type.
Note: this topic is selected from openjudge website http://noi.openjudge.cn/ch0103/10/ .
answer：If there is no answer, please comment