public static int diagonalDifference(List<List<Integer>> arr) {
    // Write your code here
    
    int size = arr.size();

    int primary = 0;
    
    int secondary = 0; 
    
    for(int i=0; i < size; i++){
        
        primary += arr.get(i).get(i);
        secondary += arr.get(i).get(size-1-i);
    }
    
    return Math.abs(primary-secondary);

    }