This is my solution:
-------------------------------------------------------
.....int a, b;
.....string s;
.....s = Console.ReadLine();
.....a = Int32.Parse(s.Substring(0, s.IndexOf(" ")));
.....b = Int32.Parse(s.Substring(s.IndexOf(" ")));
.....Console.WriteLine("{0}", a + b);
-------------------------------------------------------
Are there some easier way to read two integers without Console.ReadLine(); or somthing else, if they are stored in the same line with space:
100 200
I think that
a = Int32.Parse(s.Substring(0, s.IndexOf(" ")));
is not good solution in this case.

String[] numbers = Console.ReadLine().Split(' ');
try {
Console.WriteLine(Int32.Parse(numbers[0]) + Int32.Parse(numbers[1]));
}
catch {}

politeh rulit