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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main(void) {
   int a, b, c, area;

   scanf("%d %d %d", &a, &b, &c);
   if((a >= 1) && (a <= 100) && (b >= 1) && (b <= 100) && (c >= 1) && (c <= 100)) {
      if((a >= b) && (a >= c)) {
         area = (b * c) / 2;
      }
      else if((b > a) && (b > c)) {
         area = (a * c) / 2;
      }
      else {
         area = (a * b) / 2;
      }
      
      printf("%d\n", area);
   }
   

   return 0;
}