from itertools import accumulate
def main():
    N = int( input())
    A = list( map( int, input().split()))
    F = [0]
    B = [0]
    for i in range(N):
        F.append( A[i*2] - A[i*2+1])
        B.append( A[N*2-1-i*2] - A[N*2-2-i*2])
    AF = list( accumulate(F))
    AB = list( accumulate(B))
    ans = AF[-1]
    for i in range(N):
        if AF[i] + AB[N-i] > ans:
            ans = AF[i] + AB[N-i]
    print(ans)
if __name__ == '__main__':
    main()