Problem:
Score : 100 points

Problem Statement

There is a right triangle ABC with ∠ABC=90°.

Given the lengths of the three sides, |AB|,|BC| and |CA|, find the area of the right triangle ABC.

It is guaranteed that the area of the triangle ABC is an integer.

Constraints

1 \leq |AB|,|BC|,|CA| \leq 100

All values in input are integers.

The area of the triangle ABC is an integer.

Input

Input is given from Standard Input in the following format:

|AB| |BC| |CA|

Output

Print the area of the triangle ABC.

Sample Input 1

3 4 5

Sample Output 1

6

This triangle has an area of 6.

Sample Input 2

5 12 13

Sample Output 2

30

This triangle has an area of 30.

Sample Input 3

45 28 53

Sample Output 3

630

This triangle has an area of 630.

Solution in C (Clang 10.0.0) (judge verdict: Wrong Answer)

#include <stdio.h>

int main () {
    float ab = 0;
    float bc = 0;
    float ca = 0;
    float area = 0;
    
    printf("Please Input Length AB ");
    scanf("%f", &ab);
    
    printf("Please Input Length BC ");
    scanf("%f", &bc);
    
    printf("Please Input Length AC ");
    scanf("%f", &ca);
    
    area = ((ab*bc)/2);
    
    printf("%f", area);
    
    return 0;
}