def jian(a,b):
    return a - b

n = int(input())
a = list(map(int,input().split()))

if n % 2 == 0 :
    l1 = a[:(n//2)]
    l2 = a[(n//2):]
    l2.reverse()
    l = list(map(jian,l1,l2))
else:
    l1 = a[:(n // 2)]
    l2 = a[((n // 2) + 1):]
    l2.reverse()
    l = list(map(jian, l1, l2))

while i < (len(l) - 1):
    q += abs(l[i])
    if l[i] * l[i+1] > 0:
        if abs(l[i]) >= abs(l[i+1]):
            i += 1
        else:
            l[i + 1] += abs(l[i]) * (abs(l[i+1])//l[i+1])
    i += 1
    
q = 0
i = 0
if i == (len(l) - 1):
    q += abs(l[i])
print(q)