Diagonal Difference

using System;
using System.Linq;
class Program
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine());

        long[][] matrix = new long[n][];
        // Filling the Matrix
        for (int row = 0; row < n; row++)
        {
            matrix[row] = Console.ReadLine().Split().Select(long.Parse).ToArray();
        }

        // Sum the first diagonal of Matrix
        long firstDiagonalSum = 0;
        for (int row = 0; row < n; row++)
        {
            for (int col = 0; col < n; col++)
            {
                if (row == col)
                {
                    firstDiagonalSum += matrix[row][col];
                }
            }
        }

        // Sum the second diagonal of Matrix
        long secondDiagonalSum = 0;
        for (int row = 0; row < n; row++)
        {
            for (int col = n - 1; col >= 0; col--)
            {
                if (col == Math.Abs(row - n + 1))
                {
                    secondDiagonalSum += matrix[row][col];
                }
            }
        }
        Console.WriteLine(Math.Abs(firstDiagonalSum - secondDiagonalSum));
    }
}