Basics Exam 10 April 2014 Morning 02.Half Sum

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class HalfSum
{
    static void Main()
    {
        int n, firstNumber, secondNumber;
        int firstSum = 0;
        int secondSum = 0;
        do
        {
            n = int.Parse(Console.ReadLine());
        } while ((n >= 0)^(n <= 500));
        for (int i = 0; i < n; i++)
        {
            do
            {
                firstNumber = int.Parse(Console.ReadLine());
            } while ((firstNumber >= -500000)^(firstNumber <= 500000));
            do
            {
                secondNumber = int.Parse(Console.ReadLine());
            } while ((secondNumber >= -500000) ^ (secondNumber <= 500000));
            firstSum += firstNumber;
            secondSum += secondNumber;
        }
        if (firstSum == secondSum)
        {
            Console.WriteLine("Yes, sum="+ firstSum);
        }
        else
        {
            int difference;
            if (firstSum > secondSum)
            {
                difference = firstSum - secondSum;
            }
            else
            {
                difference = secondSum - firstSum;
            }
            Console.WriteLine("No, diff="+difference);
        }
    }
}