PROGRAMMING:Lovely Tommy (error correction version)
John takes his dog Tommy to meet his girlfriend Mary, and they set out to meet each other at the same time. Tommy runs fast, runs back when he meets Mary, runs back when he meets John,... Until they meet. Excuse me: how many miles did Tommy run?
####Input format
>Distance between two people at the beginning ($$km $$)
>Speed of John, Mary and Tommy ($$km / h $$)
####Output format
>Tommy's distance ($$km $$)
Requirement: output 2 decimal places (round the last place).
####Input sample
```in
sixty-nine point seven five
5.1 4.9 10.2
```
####Output sample
```out
seventy-one point one five
```
---
Requirement: consider the error of real number.
answer：If there is no answer, please comment
####Input format
>Distance between two people at the beginning ($$km $$)
>Speed of John, Mary and Tommy ($$km / h $$)
####Output format
>Tommy's distance ($$km $$)
Requirement: output 2 decimal places (round the last place).
####Input sample
```in
sixty-nine point seven five
5.1 4.9 10.2
```
####Output sample
```out
seventy-one point one five
```
---
Requirement: consider the error of real number.
answer：If there is no answer, please comment