using System;

public class Program

{

    private static float TrapezoidArea(float a, float b, float h)

    {

        float x = (a + b) * h;

        return x * 0.5f;

    }

    public static void Main()

    {

        Console.Write("Side A: ");

        float a = float.Parse(Console.ReadLine());

        Console.WriteLine();

        Console.Write("Side B: ");

        float b = float.Parse(Console.ReadLine());

        Console.WriteLine();

        Console.Write("Height: ");

        float h = float.Parse(Console.ReadLine());

        Console.WriteLine();

        Console.WriteLine("The area of the trapezoid (in cm) is " + TrapezoidArea(a, b, h));

    }

}