N = int(input())
A = list(map(int,input().split()))

B = []
for i in range(N):
    a = i*2
    b = a+1
    B.append(A[a]-A[b])
now = sum(B)
maximum = now
for i in range(-1,-N-1,-1):
    now -= 2 * B[i]
    maximum = max(maximum,now)
print(maximum)