Problem:
Score : 100 points

Problem Statement

You are given a trapezoid. The lengths of its upper base, lower base, and height are a, b, and h, respectively.

An example of a trapezoid

Find the area of this trapezoid.

Constraints

1≦a≦100

1≦b≦100

1≦h≦100

All input values are integers.

h is even.

Input

The input is given from Standard Input in the following format:

a
b
h

Output

Print the area of the given trapezoid. It is guaranteed that the area is an integer.

Sample Input 1

3
4
2

Sample Output 1

7

When the lengths of the upper base, lower base, and height are 3, 4, and 2, respectively, the area of the trapezoid is (3+4)×2/2 = 7.

Sample Input 2

4
4
4

Sample Output 2

16

In this case, a parallelogram is given, which is also a trapezoid.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.PrintWriter;
import java.util.Scanner;

public class Main {
    static private Scanner scan = new Scanner(System.in);
    public static void main(String args[]) {
        int int1 = Integer.parseInt(scan.next());
        int int2 = Integer.parseInt(scan.next());
        int int3 = Integer.parseInt(scan.next());
//        String temp_str1 = "";
//        String temp_str2 = "";
        int temp_int1 = 0;
//        String str1 = scan.next();
//        String str2 = scan.next();
//        String str3 = scan.next();
        int ans_int = 0;
        String ans = "";
//        double ans_dob = 0;
        ans_int = ((int1+int2)*int3)/2;
        PrintWriter out = new PrintWriter(System.out);
        out.println(ans_int);
        out.flush();
        scan.close();
    }
}