PROGRAMMING:Find the area of triangle
Input the length of the three sides of the triangle and calculate its area.
###Input format:
Enter three real numbers that can form a triangle in one line, separated by commas.
###Output format:
For each group of input, the area value is output in one line, and the result retains two decimal places without additional characters.
###Input example:
```in
3,3,3
```
###Output example:
```out
three point nine zero
```
answer：If there is no answer, please comment
###Input format:
Enter three real numbers that can form a triangle in one line, separated by commas.
###Output format:
For each group of input, the area value is output in one line, and the result retains two decimal places without additional characters.
###Input example:
```in
3,3,3
```
###Output example:
```out
three point nine zero
```
answer：If there is no answer, please comment