import collections
N = int(input())
lsA = list(map(int,input().split()))
lssumf = [lsA[0]-lsA[1]]
lssumr = [lsA[2*N-1]-lsA[2*N-2]]
for i in range(2,2*N,2):
    lssumf.append(lssumf[-1]+lsA[i]-lsA[i+1])
for i in range(2*N-3,-1,-2):
    lssumr.append(lssumr[-1]+lsA[i]-lsA[i-1])
lssumr.reverse()
ans = max(lssumr[0],lssumf[N-1])
for i in range(N-1):
    ans = max(ans,lssumf[i]+lssumr[i+1])
print(ans)