static void Main()
{
Console.WriteLine("Hello World");
square s = new square();
Console.WriteLine(s.area(2,4));
for(int a = 0 ; a < 2; a++ )
{
Console.WriteLine("a is :"+a);
}
circle c = new circle();
Console.WriteLine(c.area(10));
triangle t = new triangle();
Console.WriteLine(t.area(10,5));
string str = "Ruan";
Console.WriteLine(str.ToLower());
}
