public static int diagonalDifference(List<List<int>> arr)
    {
        int finalresult = 0;
        
        for(int i = 0; i < arr.Count(); i++){
            finalresult += arr[i][i] - arr[i][arr.Count() - i - 1]; 
        }
        
        return Math.Abs(finalresult);
    }