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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;
 
class Main {
 
public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		// get a integer
		int num1 = sc.nextInt();
		int num2 = sc.nextInt();
		
		int total = getAreaTriangle(num1,num2);
		
		System.out.println(total);
	}
	
	public static boolean isMaxNum(int num) {
		return num > 100 ? true : false;
	}
	
	
	public static int getAreaTriangle(int num1,int num2) {
		
		if(isMaxNum(num1) || isMaxNum(num2) ) {
			return 0;
		}
		
		return  (num2 * num1) / 2; 
	}
	
}