here's my code.Please give me some advise or test data!

            int n = int.Parse(Console.ReadLine());
            int nCopy = n;
            int sum = 0;
            string[] array = new string[2];
            short digitSum = 0;
            while(n-- != 0)
            {
                digitSum = 0;
                array = Console.ReadLine().Split(' ');
                foreach(var i in array)
                {
                    digitSum += short.Parse(i);
                }
                sum += digitSum * (int)Math.Pow(10, n);
            }

            Console.WriteLine(sum.ToString().Length > nCopy ? sum.ToString().Substring(1):sum.ToString().PadLeft(nCopy,'0'));

From task description:
> (1 ≤ N ≤ 1 000 000)

Why do you think you are able to put result into 32-bit (10 digits max) int variable?