#!/bin/python

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)
z1,z2 = 0,0
for x1 in range(n):    
    z1 += a[x1][x1]
for x1 in range(n):
    z2 += a[x1][n-x1-1]

print z1,z2
'''
n = int(input().strip())
dSumLeft = 0
dSumRight = 0
for i in range(n):
    matrixRow = input().split()
    dSumLeft += int(matrixRow[i])
    dSumRight += int(matrixRow[-(i + 1)])
print dSumLeft-dSumRight