using System;
public class Program
{
public static void Main()
Console.WriteLine("a=");
Console WriteLine("a="); int a=int.Parse(Console.ReadLine());
Console WriteLine("b=");
int b=int.Parse(Console.ReadLine());
console-writeLine("h-"); int h-int.Parse(Console.Readtine());
double s-(a+b)*h/2;
Console WriteLine ("s="+s);
}
