I have no idea how to read this input data, because i don't know when to stop reading...any help please.

string line;
while((line = Console.ReadLine())!=null){
   //...code here...
}

A simple approach is using-
String input = Console.In.ReadToEnd(); //Press Ctrl+Z and hit enter to mark the end of input

Refer to http://acm.timus.ru/help.aspx?topic=csharp