static int[] ar1 = new int[] { 4, 5, 3 };
        static int[] ar2 = new int[] { 5, 7, 8};
        static int[] ar3 = new int[10];

        static void Sum()
        {
            int c = 0;
            int i = 0;
            while (i < ar1.Length && i< ar2.Length)
            {
                int d = ar1[i] + ar2[i];
                if (d >= 10)
                {
                    d %= 10;
                    ar3[i] = d + c;
                    c = 1;
                }
                else
                {
                    ar3[i] = d + c;
                    c = 0;
                }
                i++;
            }
            if (ar1.Length > ar2.Length)
            {
                int a = i;
                for(; a<ar1.Length; a++)
                {
                    ar3[a] = ar1[a] + c;
                    c = 0;
                }
                i = a;
            }
            if (ar2.Length > ar1.Length)
            {
                int a = i;
                for(; a < ar2.Length; a++)
                {
                    ar3[a] = ar2[a] + c;
                    c = 0;
                }
                i = a;
            }

            Console.WriteLine();
            int j = i-1;
            if (c == 1)
            {
                ar3[i] = 1;
                j = i;

            }
            for (; j>=0 ; j--)
            {
                Console.Write(ar3[j]);
            }
            Console.WriteLine();
        }

        static void Ar(int[] a)
        {
            for (int i = a.Length-1 ; i>=0  ; i--)
                Console.Write(a[i]);
        }
        static void Main(string[] args)
        {
            Ar(ar1);
            Console.WriteLine();
            Ar(ar2);
            Sum();