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

cL = [0]*(n+1)
cR = [0]*(n+1)

L = []
R = []
for i in range(2*n):
    if i%2 == 0:
        L.append(A[i])
    else:
        R.append(A[i])

R.reverse()
for i in range(n):
    cL[i+1] = cL[i]+L[i]
    cR[i+1] = cR[i]+R[i]

ans = 0
for i in range(n+1):
    j = n-i
    ans = max(ans, cL[i]+cR[j])
print(2*ans-sum(A))