#N = "3"
#A=[]
#A[0] = "11 2 4"
#A[1] = "4 5 6"
#A[2] = "10 8 -12"

forwardDiag=int(0)
backwardDiag=int(0)
N = raw_input()
for i in range(0,int(N)):
	A=[]
	A=raw_input()
	A=A.split()
	forwardDiag=forwardDiag+int(A[i])
	backwardDiag=backwardDiag+int(A[(int(N)-1)-i])

print abs(forwardDiag-backwardDiag)