from itertools import accumulate
N = int(input())
A = list(map(int,input().split()))
if N == 1:
    print(max(A)-min(A))
    exit()
B = []
for i in range(0,2*N-1,2):
    B.append(A[i]-A[i+1])

BC = list(accumulate(B))
ans = 0

for i in range(len(BC)):
    ans = max(ans,BC[i]-(BC[-1]-BC[i]))
print(ans)