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 1.8.0) (judge verdict: Accepted)


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.StringTokenizer;

public class Main {


    public static void main(String[] args) throws IOException {
        Scanner s = new Scanner(System.in);
        System.out.println(s.nextInt()*s.nextInt()/2);

    }




}


class Scanner
{
    StringTokenizer st;
    BufferedReader br;

    public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}

    public String next() throws IOException
    {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine());
        return st.nextToken();
    }

    public int nextInt() throws IOException {return Integer.parseInt(next());}

    public long nextLong() throws IOException {return Long.parseLong(next());}

    public String nextLine() throws IOException {return br.readLine();}

    public double nextDouble() throws IOException
    {
        String x = next();
        StringBuilder sb = new StringBuilder("0");
        double res = 0, f = 1;
        boolean dec = false, neg = false;
        int start = 0;
        if(x.charAt(0) == '-')
        {
            neg = true;
            start++;
        }
        for(int i = start; i < x.length(); i++)
            if(x.charAt(i) == '.')
            {
                res = Long.parseLong(sb.toString());
                sb = new StringBuilder("0");
                dec = true;
            }
            else
            {
                sb.append(x.charAt(i));
                if(dec)
                    f *= 10;
            }
        res += Long.parseLong(sb.toString()) / f;
        return res * (neg?-1:1);
    }

    public boolean ready() throws IOException {return br.ready();}


}