PROGRAMMING:Find the area of triangle
Given the length of the three sides of a triangle, the area of the triangle is calculated.
###Input format:
There are three real numbers in a row that represent the three sides of a triangle, separated by spaces.
###Output format:
Output the area of this triangle. Keep three decimal places.
###Input example:
```in
3 3 3
```
###Output example:
```out
three point eight nine seven
```
answer：If there is no answer, please comment
###Input format:
There are three real numbers in a row that represent the three sides of a triangle, separated by spaces.
###Output format:
Output the area of this triangle. Keep three decimal places.
###Input example:
```in
3 3 3
```
###Output example:
```out
three point eight nine seven
```
answer：If there is no answer, please comment