# 区間dpだと間に合わない、左右からの累積和で解ける
# 左からのネット得点累積和、右からのネット得点累積和
# どこまで左、どこまで右なら最大値となるか

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

from_left = []
for i in range(N):
    calc = A[i*2]-A[i*2+1]
    from_left.append(calc)
from_left_cumu = [0]
temp = 0
for i in range(N):
    temp += from_left[i]
    from_left_cumu.append(temp)
    
#print(from_left)
#print(from_left_cumu)

from_right = []
for i in range(N):
    calc = A[N*2-i*2-1]-A[N*2-i*2-2]
    from_right.append(calc)
from_right_cumu = [0]
temp = 0
for i in range(N):
    temp += from_right[i]
    from_right_cumu.append(temp)
from_right_cumu.reverse()
    
#print(from_right)
#print(from_right_cumu)

ans = -10**20
for i in range(N+1):
    ans = max(ans, from_left_cumu[i]+from_right_cumu[i])
print(ans)