ارسال شماره 131

n= int (input())
str = input()
numberstr = str.split()
number = [int(numbers) for  numbers in numberstr ]
j = n 
count = 0
   
for i in range( n // 2):
    j = n - 1 - i 
    count += abs(number[i] - number[j])
    
            
print(count)