#!/bin/python

"""
Input Format:
The first line contains a single integer. The next lines denote the matrix's rows, with each line containing space-separated integers describing the columns.

Output Format
Print the absolute difference between the two sums of the matrix's diagonals as a single integer.

Sample Input
3
11 2 4
4 5 6
10 8 -12

Sample Output
15

Explanation

The primary diagonal is:
11
      5
            -12

Sum across the primary diagonal: 11 + 5 - 12 = 4

The secondary diagonal is:
            4
      5
10
Sum across the secondary diagonal: 4 + 5 + 10 = 19
Difference: |4 - 19| = 15
"""

import sys

n = int(raw_input().strip())
a = []
for a_i in xrange(n):
    a_temp = map(int,raw_input().strip().split(' '))
    a.append(a_temp)

print abs(sum([(a[i][n-i-1] - a[i][i]) for i in range(n)]))