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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;
import java.io.*;
import java.lang.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner (System.in);
		int a = sc.nextInt(); int b = sc.nextInt(); int c = sc.nextInt();
		int max = max (a, b, c);
		int prod = 1;
		if (a != max) {
			prod *= a;
		} 
		if (b!=max) {
			prod *= b;
		}
		if (c != max) {
			prod *= c;
		}

		System.out.println(prod/2);
	}

	public static int max (int a, int b, int c) {
		int max = a;
		if (b > a) {
			max = b;
		}
		if (c > b) {
			max = c;
		}

		return max;
	}
}