static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        int[][] a = new int[n][];
        for(int a_i = 0; a_i < n; a_i++){
           string[] a_temp = Console.ReadLine().Split(' ');
           a[a_i] = Array.ConvertAll(a_temp,Int32.Parse);
        }
        
        int totalSum=0;
        int j=n-1;
        for(int i=0;i<n;i++){
            totalSum=a[i][i]-a[j][i]+totalSum;
            j--;
        }
        
        Console.WriteLine(Math.Abs(totalSum));
    }