public static void Main(String[] args)
if ((result<0 && n>0) || (result>0 && n<0)) {
Console.WriteLine("input firstnum");
firstnum = int.Parse(Console.ReadLine());
Console.WriteLine("input secondnum");
secondnum = int.Parse(Console.ReadLine());
Console.WriteLine("Expected Output: "+ firstnum + secondnum);
Console.WriteLine("Expected Output: "+ firstnum - secondnum);
Console.WriteLine("Expected Output: "+ firstnum * secondnum);
Console.WriteLine("Expected Output: "+ firstnum / secondnum);
Console.WriteLine(mod("Expected Output: "+ firstnum, secondnum));